khoney

Fellow Rotorites,
I've been working this problem for a while now,and have fixed some other idling problems along the way, but this one is getting the best of me. I don't want to try things at random (could get expensive), so here's a detailed description of the problem:

I am getting random VIOLENT hesitations at various RPMs and speeds (can happen in multiple gears). It seems to get worse with higher outdoor temps (90 and above). When it happens, I can hear rapid exhaust farts (a more technical term escapes me ). It is MUCH more violent than simply removing and reapplying throttle, in fact it can throw me forward in my seat, almost like stomping on the brakes. Of course, I immediately take my foot off the gas and cautiously reapply it. The problem occurs mostly between 2K and 3K RPM (max torque?)

I have:
1) Replaced the Bypass Air Solenoid Valve (only because I broke off a hose nipple while removing the intercooler).

2) Adjusted the throttle stop screw (was not making contact at all when at idle)

3) Readjusted the TPS (LED method)

4) Replaced spark plugs

The car had also had problems with wanting to die at idle and a bouncing idle. The above work seems to have fixed all that. It is now idling fine, still occasionally wants to die prior to a good warmup when the AC is turned on (lazy BAC?)

Anyway, here are my suspects:
1) Bad plug wires (never been replaced)

2) Clogged injector (I think I have a leaky one anyway, always need to pull the EGI fuse to do a hot start)

3) Misfiring?

4) Problem with TPS only when hot (looks OK when warm, no discontinuities in resistance, LEDS behave properly.

5) Bad ECU ground (would there be other symptoms I could check for???)

I was thinking of running an extension cable from the TPS check connector into the car so I can look at the LEDS when the hesitation occurs. I'm not sure though if that would isolate the TPS (i.e. could the LEDs also be affected by an ECU ground problem)?

It's got 140K miles, almost everything is original. Only fuel/systems emissions replacements are fuel filter and ABSV. I'm hoping to get some advice from the experts on what to check (and in which order!) What do you think is most likely to be the problem, and are there things not on the list that I should check? Thanks in advance for your help!

Everyone tells me "If you're having so many problems, why don't you just get a new car?". They just don't understand...

Kevin (would cry to see someone else drive it away...)

vaughnc

I had that on my 92 TII. Turned out the intake manifold was warped and the intake pipeing was cracked. According to Mazcare - the O2 sensors were seeing a rich (or lean) condition when there wasn't one due to the cracks.

Replaced the manafold and taped over the cracks.

I was getting a check engine light though - the error codes were water thermo and both O2 sensors.

If it isn't the 3500 rmp hesitation/electrical ground problem, I'd suspect the above.

akageals

My car was doing this when the BAC wires shorted out on metal in the engine compartment...the plug had disintegrated. It shorts out the ignition until the wire falls away from the metal...it eventually broke the fuse and I was able to find it.

Todd

hypntyz7

Sounds like a bad TPS to me. IF youve adjusted it(try using a dmm to adjust it to 1kohms(black and pink leads)) then get another one, or if you can afford it a new one. IF you have any friends with FCs(86-8) then ask to borrow theirs for a few minutes. Do not fool with the adjustment on their car, only when you put their TPS on yours. IF it works fine on another one, and you put it on yours and sdjust it, it should work if that is the problem. I would check here first, and Ive worked on about 20 FC's of my own.BTW turbo and NA tps' are the same in 86-8

khoney

OK, the latest news on the violent hesitation problem that is REALLY starting to **** me off.

Replaced the TPS and the air funnel hose that had a crack in it. Idle seems to be fine now. The hesitation problem is STILL THERE. It is intermittent. I drove around town last weekend, and it was happening all the time, various amounts of throttle, various gears. When it happens, the TPS check connector LEDS show IDLE even though the throttle is NOT at idle. Sometimes one of them rapidly blinks on and off. I took a road trip last weekend (150 miles one way, all highway). First 30 miles had the hesitation problem BIG TIME, then it STOPPED and didn't happen for the rest of the trip. When I drove back, it was fine all the way. Drove fine to and from work yesterday. Was fine this morning. Coming home tonight I felt like I was riding the mechanical bull! I have no idea where to go from here. The mechanic checked grounds, found no problems there. Does anyone know exactly how the TPS works? In other words, what can cause the TPS to go bonkers OTHER than a bad TPS? I just put $1500 into this car and am really getting frustrated.

vaughnc

bump

MaxRX7

air filter !!!

spinner26

try a new fuel filter. been there..

with it clogged full of debris it will funk you up at all rpm's

HAILERS

1. Try driving with the tps disconnected. Does it still have violent hesitation.
2. Or, hook your meter to the output of one of the secondary injectors. It will read about 12v until the secondaries come into play, then the voltage should drop to 8-9volts.
3. I have had VIOLENT HESITATION due to the injector plugs having been in a fire and the previous owner splicing(not soldering) new plugs on. The splices corroded and caused a loss of ground from the ECU.
4. Several people on this site have had violent hesitation due to no orfice (pill) in the vacuum line to the boost sensor(pressure sensor). Keith is one.
5. Personal predjudice says its electrical in nature and involves the loss of ground to the injectors(secondary injectors).
6. Could be any one of the posts above this one or one of those following this one.
7. Monitoring the tps while driving is not worth doing using the leds. Better to use a meter on the output of the tps to the ECU. I think its 2g (no schematic at work). All personal predjudice. Could be wrong. Could be right. Your call. Tps should be approx 1 volt at idle and about 4.65 at max output which comes prior to wot.

khoney

The air filter is a K&N and was recently cleaned. The fuel filter up front was replaced early on to try to correct this problem. I have not replaced the one by the fuel tank, nor have I ever replaced the fuel pump (140K miles). Like HAILERS, I suspect something electrical as well.

The hesitation can occur while cruising at under 3K, very little throttle applied. Are the secondaries even on under this condition?

The problem SEEMS to show up after stopping and restarting when hot.

Could the problem be due to really leaky or really clogged injectors? Never been cleaned, other than Techron in the tank.

If I was running very rich, could this problem result?

To get a good ground to the injectors and TPS, what is the recommended approach (the ground strap should go from where to where)?

HAILERS, if I did monitor the TPS and/or the secondaries and the voltage went haywire, what would that prove? Would It definitely be narrowed down to a bad ECU, a bad ground, or a bad signal wire?

Thanks in advance for the advice and for sticking with me on this.

BTW, I get bad popping sounds (afterburn?) every time I let off the throttle, especially when the engine is cold. I do not have a primary cat. Does this shed any light?

Kevin

Six Rotors

iTrader: (17)

Khoney,you have to remember that the TPS test light connector and test light is used to test other things beside the TPS.If you check out the FSM,particularly Sect 4B-44,for example,you will get an idea of what I mean.
I can suggest 2 really cheap things to try:
1-look in the boost sensor hose to ensure you have the pill in place--pull the hose at the ACV end and the pill should be about an inch down the hose.If it is not there get one from Mazda~$2.
2-Pull the connector at your TPS,on the harness side you have 3 wires,Black(depending on year may have brown or white stripe),Brown with white stripe,Green with red stripe.With your ignition switched on measure the voltage on the Brown/white stripe wire to ground on the motor somewhere-- should be 4.5-5.5 volts.If that's OK,Next take a piece of wire,18 inches long,bare it each end,connect one end into the Black wire(under the connector will do fine for now)and reconnect your TPS.Take the other end of the wire and connect it under a bolt,say the one on the filler neck where the accelerator cable bracket is--make sure it is really clean because this will be your new ground for the TPS.Try it if your problem has gone you had a bad ground circuit to your TPS.
Other possibilities are bad ground at the boost sensor and the AFM and can be treated in a similar way.

Six Rotors

iTrader: (17)

This a PS--I should have suggested that you buy a can of contact cleaner and a tube of dielectric grease and clean and grease all the connectors you can see on the engine.

HAILERS

Happens under 3000 with a steady throttle? In that case I'd do what Six Rotors suggests. Your right. Under 3000 and not flooring the pedal, I don't see the secondaries playing a role either. Sorry. Misunderstood when it was happening. Darn. Could be the wires to one of the primary injectors intemittantly touching each other due to rotted and overheated wiring(brittle). Yeah. Do the grounds. If you look at the wiring schematic Bb-2 in the 87 factory manual you'll see that the tps, boost sensor, airflow meter, intake air temp sensor, water thermo sensor, variable resistor, all have their grounds tied together or spliced together. So it would seem if you do what Six Rotors says about grounding the tps a second time, so to speak, you'll also be giving the aforementioned devices a better ground also. That is all dependent on the schematic being correct. They all splice together and go to the ECU on pin 2c on a 87.That said, yours sounds much different than the usual writeup which talks about a *hesitation*. I believe you said or used the word Violent. Makes you wonder. Yup, pill and ground with checking the connectors to the air flow meter and boost sensor. And I know someone wants to write and tell you about the ground wires that are grounded to the engine under the intake. Important grounds. And I'd forget about monitoring the secondary injectors since the secondary injectors do not seem to be the prob.

HAILERS

Another idea. I re-read your second post and you mention the grounds for the injectors. The way I understand it, one wire on your injectors is 12 volts. Its there all the time. The ECU supplies the ground to turn the injectors on and off. So the IDEA I guess would to do what several folks on this site suggest, which is to go to the ECU and solder on to the ground wires on the plugs and create a new or additonal ground near the ECU. Another thought that occured concerned the fuel pump and the possibility of the micro sw in the air flow meter being corrupt and switching the fuel pump off even though the afm door is open(you do have a 87 or 88?). You could jumper that fuel pump check plug on the right hand strut tower to bypass the afm sw and go for a ride. Six Rotors has written before on a post about taking a logical approach to solving a problem, so perhaps you should start with the things he suggested and if they do not work out make a list of the things on this post from everyone and do one at a time. The Violent HESITATION is throwing me off a bit. Its just not the normal hesitation, which is just that, a hesitation, not a throw me into the steering wheel hesitation. Oh well, have fun. Better you than me. Humor.

khoney

Thanks much, guys! Looks like yet another weekend shot to hell!

khoney

HAILERS, I read your response to my question under the TPS checker thread. Thought I'd hop back over to continue. OK, let's explore this further. I get thrown into the steering wheel when the LED checker shows the valves are in an idle state when they're not. I checked my ground today from the TPS to 1) the connection at the passenger side firewall and 2) the negative battery terminal. I get 0.1 ohms, which is about as good as you can ask for. So if the relief and solenoid switching states don't matter, then whatever is causing this problem is ALSO causing the solenoids to switch to the wrong state. You had mentioned the AFM and boost mods - my mechanic checked the grounds at both places last time I had it in the shop, he said both were good. The boost shouldn't matter, because this happens under zero boost anyway. And wouldn't the fule cut just make it act like that car's running out of gas? That doesn't reelly result in a violent hesitation. I guess I could try throwing my fuel cut switch while driving - would this duplicate that AFM ground problem scenario?

Sooo, I guess my question would then be what does the ECU look at when determining how to set the relief and switching solenoid valves? If it is JUST the TPS, my TPS has been replaced and the ground seems to be good. And what does it do when it thinks its at idle that would throw me into the steering wheel? If it is fuel cut, I wouldn't expect the valves to go to their idle state. If the primary injectors have an intermittent ground, that can explain the hesitation but not the valve states, since the injectors are controlled by an output only and there is no feedback to the ECU regarding injectors (or is there?). It seems to me that something must be telling the ECU I have gone to idle. Isn't the TPS the only indicator of that? I really am trying to be logical and methodical about this. I don't understand why the violent lurching is ALWAYS associated with the relief and solenoid valves going to their idle state. Even without the violent lurching (just a sputtering hesitation) there is always something funky happening with those valves when it happens. I guess I'm looking for an explanation for this condition, and I haven't found one yet.

HAILERS

I'm getting KHONEY and BIGWOOGIE post mixed in my pea brain. One or the other disconnected his tps and went 40 yards before it started doing the lurch, buck, slam the face in the steering wheel thing. Therefore I assumed that it cannot be the tps. Its disconnected. Right? No since looking there for a while. I can duplicate a *throws me into the steering wheel*. I've done it for another post a few months ago. It ain't hesitation. Its face in the steering wheel. I pulled both secondary injector plugs off and went for a drive. Foot to the floor. Face in the steering wheel. One follows the other. The way I understand it, the secondaries are scheduled to come on and at the same time the primaries are cut back to 60percent of their duty cycle. Well the secondaries are not a going to come on with the plugs off, so. face in wheel. I'm as lost as you are. If it were my car, I'd surrender and go to work on the injector harness. Ring both the wires to the injector plugs and make sure they are not touching. Twist and turn while monitoring the meter. Ohm them out and compare them with each other. OH! I just thought. Have either of you checked for the orfice in the boost(pressure)sensor? Once I replaced that vac hose and forgot the orfice(see PILL). Jerked me around. I'd take the plug off the afm and make sure the mating pins and sockets are good. I'd put a meter on each pin on it and wiggle that connector looking for opens. Ditto with the ECU plugs. Follow the ECU plugs from the ecu. there are connectors they go to in the passengers area. Disconnect and reconnect. My 87 when I got it and rebuilt the engine ran like a lame doggg. for the longest time. I thought the 2nd gen must be overrated. Finally by playing around connecting and disconnecting connectors(some reason I don't remember) drove the car and found about fifty more horses. They disappeared two days later. Two things were killing me. One was poorly spliced in wires to the injectors(previous owners fire fix) and adding a ground to the boost(pressure) sensor. Sorry if I'm making lite of your problem. Its going to take some checking of wiring, especially the ecu gnd under the intake manifold. Have you disconnected your tps and gone out driving? Still jerks. Ain't the tps then. (Just watch. somebodys going to write back that, that is'nt so). Not TPS, Not acv or switching and relief solenoids. Its something killing the fuel or ignition. Is your air flow meter installed in the normal position or has someone maybe placed it on its side(afm door might be causing the problem). You might go to the manual and check section 4a or 4b, look under CONTROL UNIT, which list the function of each pin and their value at idle, and check each and everone. Lot of words here, but no sure answer. I spent over a month figuering out what was wrong with that car of mine. It was in the trenches type thing and dogged determination, all of which I know you have. This was prior to my knowing about this site. Just factory manual, 80bucks and a lot of words about what Mazda engineers mothers were. Darn wipers and logicon and idiot lites and cpu and lack of solder craftsmanship by the Koreans who probably built them. Oh yes, the ECU looks at the boost sensor whether its boosting or not. The N/A also have a boost sensor(pressure sensor).

Six Rotors

iTrader: (17)

Since you are handy with wires etc,I would suggest you monitor the voltage output from the TPS(instead of the checker lights).It should read about 1v at idle and 4.5 v at full throttle.If you have a rational voltage when the hesitation occurs
then you know for sure the TPS is not causing your problem.
I don't know your mechanic,but I would sure like to know how he determined the grounds were OK at the other sensors.
By the way you should know it took me over a year of screwing around with my 10AE to eliminate my hesitations.(Grounds at the TPS and pressure sensor)

Six Rotors

iTrader: (17)

PS.When I did my trouble shooting the only resistance to ground I accepted(finally )was 0 ohms.

khoney

I checked my boost sensor ground and am getting abut 1.6 ohms. Don't know if this is 'bad' enough to cause a problem. BTW, I did drive the car without an orifice for about a week or so ( it broke after removing the hose), until i found out that I needed one. I got one from Mazda and some silicone hose. Does it matter which direction the orifice is inserted? There were no instructions.

I also made a huge dumb-*** mistake a while back and connected a spare boost sensor ground wire to the +12 on the sensor instead of GND. Blew my EGI fuse. Don't know if the boost sensor is still OK (the gauge seems to work, if that matters). Anyway, I was having the violent hesitations BEFORE all this happened.

BTW, it doesn't look like my thermowax is taking the cam off the roller when the car is warmed up. It ends up with the edge of the cam on the midpoint of the roller. Does the car need to be real hot for it to come completely off, or just at normal operating temp? Is this something I should worry about?

Six Rotors

iTrader: (17)

1-I think it probably does.Adding anew ground is easy.
2-According to Mazda it is important where you locate the orifice.It should be about 1 inch down the vac hose at the end which goes onto the nipple at the ACV.
3-The cam should clear the roller,ie there should be daylight between the roller and the curved edge of the cam.The car should be at its normal operating temperature.You may also want to inspect the coolant passage through the thermowax.Some people have reported plugged or partially plugged water passage which results in inconsistent clearance of the roller and cam.You should worry about it because if the roller is not clear of the cam it is impossible to set up your TPS correctly.

khoney

I have the orifice in the right location, but I was wondering if it made a differents which way it is inserted. One end of it has a larger hole than the other.

I will try the new ground.

I took the cam off the roller before adjusting the TPS, so I think I'm ok with the adjustment.

BTW, I remember reading a post from someone who suggested and easier way to bypass the intercooler than the PVC pipe setup. I think it had to do with disconnecting something. I can't find the post now (should've bookmrked it). Anyone remember what it was?

copandengr

I had a severe hesitation problem on my '86 NA. After pulling all my remaining hair out I discovered the alternator wasn't putting out enough voltage. It was only managing about 12.5 volts. It should be 13.8V. It seems that the injectors and other engine managment systems are very sensitive to low voltage.

As temperature has an adverse affect on your voltage regulator this might be an advisable thing to check.

This low voltage (if it exists) might be caused by anything from a bad voltage regulator to a bad ground to a slipping belt. Be sure to check all possibilities, and check your alternator output at higher RPMs and heavy loads. A slipping belt might not show up at idle speeds or light electrical loads.

HAILERS

KHONEY... You asked if there was more than the tps involved in the operation of the switching and relief valves. I can answer with certainty that the answer is YES in spades. I disconnected the vac hose from the boost sensor on my N/A and plugged it. Then went a driving. The relief valve solenoid stayed energized almost constantly where as prior it basically would only be energized when I reached about 3500rpm. I had been, prior to the disconnect of the boost hose, been monitoring the output of the relief solenoid in fifth gear, and could'nt help but notice that on a level or downhill road the solenoid would not energize until about 3500, BUT if I was on an upgrade it would energize even at 2500. It was more than the tps by itself causing this, so I pulled over and disconnected the vac hose off the boost sensor and walla, thing was virtually energized all the time. Just some low rpm was it de-energized. Also I came across a site http://www.howstuffworks.com/fuel-injection.htm that has a subheading *engine controls and performance chips* that talks about the boost(pressure)sensor. So if you were observing the tps checker lites and noticed an odd pattern, its supposed to be like that. Load sensing from the boost sensor(actual boost # not required) will turn the relief solenoid on at odd times. Probably the swithching solenoid also, but I did not check that solenoid.

Blowtus

have you had any progress khoney? I have what sounds like exactly the same problem. I'm yet to get as in depth as you... but have checked a bunch of stuff and added grounds to a few things...

Charlie