Please HELP and thanks in advance!

My car: 1991 13B Vert N/A

My problem: Car has been running great last 7,000 miles. This morning the engine light comes on and stays on. It feels as though its starting to run funny and then I THINK it dies because the Tach stops working(sitting at 0). Its actually still running so I drive another mile to see what happens. Running worse and worse. doesnt want to idle. From 0-20mph in 1st and 2nd gear starts vibrating back and forth as if someone who has never driven a stick is behind the wheel. Dies a few times(but DOES restart). I make it home and smells a bit like something burning. Pull the engine code and get a 13(intake manifold pressure sensor)

Notes I have taken from your postings:
1)Check grounding from bell housing to tranny
2)Check pressure sensor
3)Chech injector plug connections
4)Check ground to coils(especially Leading)
5)Check AFM

The only thing that has changed in the last few weeks is a new oxygen sensor and I did notice a few small backfires at high rpm between shifts after installed.

Before this, car had TONS of power.

Can anyone shed some light on whats happening.

THANKS AGAIN!

 

If the tach is not working, the trailing coils are likely not firing.

Check all the fuses first. 2nd, pull the error codes and see why that check engine light is on. Could be a dead metering oil pump, resulting in limp mode.

3rd, check for the standard massive vacuum leak on the air intake duct.

If all those check out, test compression.

 

You're on the right track.
The primary ground is common to all your symtoms.
Also check & clean all the trailing & leading coil connectors.

BTW - Good job reading ahead, & good descriptive post.

Welcome to the forum..

 

Thanks for your help Guys! I'll get to work on it as soon as I get home.

A few more things...

The last time I started it in the driveway before leaving, the tach was working again. Can the coil/ground problem be intermittent? Also, last night during very heavy tornado warnings I had a lighning bolt that scared the **** out of me that seemed to be right in front of the house(where the 7 is parked), the power in the house went off for a moment. Any way this could effect my car?

Thanks!

SURESHOT... in your photo I see that your driving lights are on without the headlights, was this an easy rewire. Mine come on only when the headlights are on.

 

That storm was crazy last night, if you get the car fixed, bring it out to the varsity

 

FOLLOW UP...

Ok guys Here is what I have done and the results...

Pulled the coils, cleaned all the grounging areas and tested with multimeter. One of the coils seems to have less resistance than the others however it was over .2 so It seemed satifactory. Reinstalled the coils and grounded them per grounding posting in the archives. Also grounded the battery from (-) battery terminal to the chassis. Added a new main ground from the (-) terminal to the transmission bolt in ADDITION to the original. NOT a replacement. Ordered and installed a known working pessure sensor from eBay. Replaced its vaccum line and put the restrictor(pill) from the old line into the new one at the same spot. Tested and cleaned the BAC while I was at it.

Result...

Once again the car starts fine and idles pretty good. Still seems to fluctuate between 650 and 750rpm sometimes. Test drive the car and seems to run as before(Good) after about 20 minutes of hard driving engine light comes on, I drive back home and the Tach does the same thing again, stops working and dummy lights come right as I enter the driveway. Turn the car off, make sure the plug wires are tight, wait a minute and crank again. Tach works and engine light is gone. I drive the car to work today. Starts fine, Idles. about 20 minutes into my drive there comes the damn engine light again but everything else works fine and I make my 45 minute drive in stop and go traffic just fine. Pull the engine codes and get a 15 and a 17(O2 sensor again?) what the hell? The last time I got a 17 it would happen at heavy load and come on and go out pretty fast. Now it seems to come on when the car is fully heated up and stays on until I turn it off and restart.

ANY IDEAS WOULD BE APPRECIATED

 

I used a VOM at the fog light console switch to find the feed wire from the headlight switch.
Then I cut it & ran a feed from the window fuse.
When the switch is on, I get daytime running lights.

 

Of course the O2 sensor could be worn out or poisoned.

The O2 Sensor wire is shielded like an audio cable, so the signal could be shorted to the shield ground. This is common if the wire has been spliced.

It could be just a weak connection.

 

The O2 sensor is new as of 3 weeks ago. I tried to find an NGK but no one had one so I went with a Bosche. Should that matter? After replacing the O2 sensor I reset the ECU and the code was gone. I'll check and see if the wire has gotten melted. If not, should I run a wire through the firewall from the O2 sensor straight to the ECU?(BTW: where is the ECU) What do you mean by poisoned?

What do you think about this Tach thing? Is it possible for a coil to be intermittent? Should I replace the plug wires? Which Trailing coil handles the tach operation? and would that coil or plug wire being bad also cause the dummy lights to come on?

 

sounds like a bad or torn AFM and you can order anything NGK off of their website. did you get a direct fit O2 sensor or did you have to solder or have it soldered on? if it was a universal fit i would triple check the connections, especially given the high temps the wire is subjected to.

 

Firstly, the O2 sensor is universal and I just crimped it. I'll rectify that! Do you say the AFM may be bad relating to the O2 sensor or the Tach issue. Can I test the AFM by just running 12volts to it?

 

OK guys, heres the deal...

I have posted a similar thread in the past https://www.rx7club.com/showthread.php?t=441085

It did it again this weekend. Engine light and dummy lights come on, Tach quites working, car is still running but like total ****, then it shuts down. Will restart but then quit unless I hold the gas all the way down, appears to be in limp mode, occasional backfire. I limp home to pull the engine code. The engine light is just eratic, not really giving a code, I crank the car again, tach still not working, car dies, I try to pull the codes again, NOW the engine light just stays on, NO blinking at all.

Last time I let it sit for a couple of weeks while I waited on a pressure sensor per engine code, installed it car has worked great for thousands of miles.

Heres where it gets interesting... This has happened after three straight days of rain. Although I keep a tarp on my Vert when it rains. Apparently my passenger door seal is bad and the tarp had blown halfway off and I found 2 inches of standing water in the passenger footwells, under the seat and behind the seat.

The last time this happened it was after several days of rain.

Is it possible that my ECU is getting wet a going haywire. Also, is it possible for this to happen, then the ECU dries out and works fine again as last time?

Please advise

 

FYI - Computers do not work under water.
The ECU case is not water proof.

You need to pull the ECU & dry it out ASAP.
Pull the cover & blow it out with an air hose or hair dryer .

When you reinstall it, check the connectors & grounds for shinny bright metal contact.

 

I was wondering why my laptop didnt work in the shower Just kidding!

I'll go ahead and pull it out and dry it out. I'll report back as to how things work when I reinstall it. Should it be obviuos if its fried?

 

From your description, I suspect you have just enough moisture inside to create some minor shorts.
Look over the PCB for corroded or bridged etches.
A little spray contact cleaner & a toothbrush may do the trick.

You may get lucky & just have some corrosion on an external ground eyelet.

 

O - Yea - & unplug the floor pan drain hole.

 

Same thing happened to mine.
Had to get a new ECU

 

Thanks a million, guys! I'll let you know what happens in a few days after I get it all dried out and put back together.

BTW, Spyder: Was it in-fact one of your door seals that was bad that allowed the water in?

 

Well right now both sides of my door seals are leaking, but only a few drips.

Someone left the top down .

 

I just cant believe that so much water can get in through the front part of the door while the whole convertible top has a tarp over it. Niether the door panel or the seat was wet so it was draining through to the bottom of the door door somehow. I guess I'll have to get a water hose out to figure it out.

 

Sureshot, I have pulled the computer and pulled it apart. It was not full of water but there was certainly moisture and droplets on both boards. As I was taking it out I noticed that the grounding eyelet was in fact VERY rusty. I will re-ground it, cover the ground with petroleum and take electronic parts cleaner and a toothbrush to the boards. I should have a result in a few days. Thanks!

 

threads merged

 

You might be looking in the wrong place for the leak. I believe there are drain holes under the hood, that might be the source. You should have two small holes on either side, one of which is a drain (the other should have a rubber plug). It's easiest to describe the location on the driver's side, since it's near the shaft for the windshield wiper. The passenger side will be a similar location.

Edit: I forgot to mention to check with your insurance company. The computer in my Audi drowned years ago due to rainwater leaking in, and my comprehensive insurance covered the repair ($1800!).

 

I'll check for the drain holes that you speak of. The insurance will not be good solution for me as I have five vehicles and recently switched to a low risk insurance carrier(Much cheaper) and I dont want to do anything to threaten that.

 

OK, after taking the ECU apart, using a blow dryer to dry it out, using electronics parts cleaner and a toothbrush to clean off some of what appeared to be white oxidation on the boards, cleaning the ECU ground and the grounding block next to the ECU, I finally got it put back in the car. So far it cranks and runs normally, the tach works and NO engine light. Hopefully nothing got fried while it was wet.

? about the leak, Has anyone had a problem with the window seal that attaches at the top of the door that touches the window as it goes down and would keep your door from filling up with water?