(sigh)....

I'm at my remote office, 30 miles from home, with a dead FD. Could use some some direction if possible.

History:
'94 touring running very well. Last night I did two things. 1) Put in a Pettit ECU and 2) plumbed a boost sensor for an upcoming AVC-R into my boost gauge vacuum line. I didn't make any other changes.

Problem:
This morning on start-up it didn't idle quite as smoothly as it does with the stock ECU. I filled it with gas and left for my office. I noticed that my boost guage was reading more vacuum than normal. I usually see 19-20 inches at idle and engine breaking, this morning I was seeing 22-24 inches. After it warmed up, I noticed that my boost gauge read a little high as well. It boosted to 14 psi primary and 10-12 secondary instead of it's typical 11 primary and 9 secondary. Because of the vacuum and boost readings, I thought it was a problem with me tapping into the boost gauge vacuum line and the gauge is reading a wider range. The car ran just fine for 25 miles, then it just quit.

The car quit while driving on the road at 55 mph. It sputtered until the car slowed down to about 2000 rpm then would start to run again (only with a lot of throttle) until I let off the gas then it would do the same thing. I barely made it to my office, the car died once and I was barely able to restart it in the parking lot by using a lot of throttle.

The noise of the backfiring brought my staff out of the office for the show. I apparently was shooting flames 3 ft from the tail pipe.

So, any ideas? I don't have my FSM, only some limited tools, and absolutely NO ideas. I looked under the hood and saw nothing amiss.

 

wow! that really sux. i mean, you did just throw in a new computer and everything is all out of whack. i would start looking at a ride home and get on the list for an engine rebuild maybe

 

Doesn't sound good to me either. The ECU is probably the reason why you were running 14lbs, but I still don't see why it would boost that high. Besides Pettit ECU's are suppossed to be capable of handling 14psi of boost. ONLY problem is do you have any fuel upgrades? If the answer is no, then I hate to say it, but you might need another engine at this point...

 

Check easy stuff first, check the map sensor line out, maybe you worked it loose when you were messing with the plumbing. Mine fell off once and the car did similar things to what you're describing (aside from increased boost). Sounds like you flooded your motor a bit too. Were you boosting when the car died?

 

That was my thought as well.

No fuel upgrades. As soon as I saw that 14 psi, I backed off. I did another run to double check and as soon as it went that high, I kept the throttle back to keep it around 10 psi.

I had just passed an RV so had boosted up to about 10 psi shortly before it died. I'll check the line to the sensor, but I never even touched the other vacuum lines, just tapped into the line that boost gauge used, which on my car is the "unused" center nipple on the UIM.

 

def check the map sensor hose, maybe it blew off with the increased boost. it will run like **** if so.

you can also try the stock ecu to see if anything improves. check the compression if the map sensor hose is fine. you could temporarily pull the lower plugs and egi, then crank it over to make sure you have 3 even pulses from each chamber. that will at least tell you if you blew an apex seal.

 

I would try to get my hands on the stock ECU and put it back in to see if it will help at all.

 

Yeah, that was my thought as well. I'm going to see if my son can drive it out to me after he is done with school today. I'd love it if that was the problem, but I don't think so. I'll look at the map sensor hose as well.

 

I hate to say it, but if you boosted 14 psi a couple of times without any supporting fuel mods you might find yourself doing a rebuild, or looking for a new motor. Hopefully we're wrong though!

 

Sounds flooded by what you describe in your work parking lot, that or the engine is blown. The pettit ecus run incredibly rich, I mean ridiculously rich. So if the plugs were on there way out then this is a possibility that you just fouled the plugs and now it is flooded. I have never fouled plugs while driving above 5mph though.

 

De-flood the engine, pull the lower plugs and pull the EGI fuse and crank it over for 10 seconds 3 times. Then try and start it again. Could just be flooded like DJ stated.

 

[quote=Dudemaaanownsanrx7;8213101]def check the map sensor hose, maybe it blew off with the increased boost. it will run like **** if so.

The hose on the map sensor had slipped down on the nipple a little bit, but wasn't off. I slid it back up.

Thanks, but I'm thinking it is toast.

Plugs are only 5 months old and looked great just over a month ago.

I'll see what I can do without any tools. I don't know why it would flood when it was being driven, although I wouldn't be surprised if it was flooded now seeing as how rich it was.

 

^^ running rich can foul out brand new plugs.

 

That would be nice if that was the problem.

 

The car died while cruising?

how many miles are on the motor? original engine?

 

Original motor (I believe), 60k miles. I had just passed an RV, boosted to about 10psi on only partial throttle. I think I was in 4th gear and topped out at only 65mph when passing them. Slowed down and about 1/2 mile down the road the car lost power and started to slow down to 2000rpm and only then would catch, backfire, and pull hard again. I would let off the gas again very quickly and as soon as I let off the gas, it would die and wouldn't catch again until about 2000rpm. Rinse and repeat for 4 miles into town.

Once the engine caught, it would pull strong until I let off the gas again. The more I describe it, the more it sounds like it wasn't getting enough fuel, yet as soon as it caught it was like the descriptions of 4th of July Fireworks, "Shoots flames and loud report".

 

could be a stuck injector maybe? Its a possibility. When you go to de-flood the engine, get some one else to crank it (with the EGI out, and Lower plugs absent) and see which plug hole most of the gas is coming out. If it is just one rotor then its possible that you have a stuck injector, and this test would tell you which rotor housing it is from.

 

Well, worst case scenario, one of your plastic fuel diffusers broke and the motor ate it. I've seen that happen twice before

 

My son arrives at the office with the Explorer and a few tools, as well as the stock ECU around 4:15pm

4:36pm: I finish with my last patient (who was late) and drive the Ex to the meeting with the contractors which was supposed to start at 4:30pm.

I make excuse to the contractors and run a few blocks down the street and rent a car dolly from Hertz Equipment Rental which closes at 5:00pm

I dash back to meet with the contractors and discuss the leasehold improvements with them for a bit over an hour. I grabbed a couple scrap pieces of 2x4 on the way out.

6:30pm: Drive the three blocks back to the office (small town) and line the RX-7 in front of the car dolly. We lay the 2x4 in front of the dolly ramps to try and get the front lip to clear. It looks like it will make it.

3 generations of guys on their way to dinner next door stop by the admire the car and offer to help push. The grandson, about 25, offers to buy the car on the spot. I'm tempted.

We push the car up, the front lip gets hung up. No way to push the car on the dolly with the lip in place. I reconsider the grandson's offer.

The guys go to dinner, and my son and I start to see if we can pull off the front lip.

It starts to rain.

We decide that it is going to be dang hard to pull the lip off with the tools at hand and even if we did, the front tire straps of the dolly won't clear the front bumper.

It starts to hail.

With nothing to loose, I decide to try swapping the stock ECU back in. I consider pulling the lower plugs to see if the engine is flooded but find that my son forgot to grab the spark plug socket. I take the negative terminal off the battery.

It starts to rain again. Harder.

I stick my head in the passenger footwell and start to unbolt the ECU bracket. Right shoulder cramps up. I get the bracket off and start to try and pull the 4 plugs on the ECU.

The wind picks up.

The bottom plug is hard to get off, try the top one. The top plug comes out without too much trouble. In fact, the top plug was really easy to get out. Thank God, it took me forever to get that plug off last night. The second plug was really easy to pull out as well. The third plug was a pain to get out. It was as hard to get out as it was last night. Fourth plug was only slightly easier to get out than it was last night. Finally got those two plugs out and pull the Pettit ECU out.

I take the stock ECU, screw on the mounting brackets, and start to plug the connectors in the ECU. The top goes in tight but makes a nice firm "click". The second one goes in with another nice "click". Third and 4th connectors go in as well. I bolt it back in and am starting to extricate my half soaked body from the car when it hits me.

The top two connectors made a nice "click". I don't remember hearing a nice "click" last night when I installed the Pettit ECU? Those top two connectors came off really easy! They were hard to get off last night.

DAMN!

I reconnect the battery and plant my soaking wet butt in the seat. Turn the key and the car cranks right up. The idle is just a tiny bit rough, but smooths out nicely after a few minutes. After parking the dolly, we drive it home with absolutely no problems.

When I passed the RV this morning, I crossed the center line that has some really massive rumble strips. My guess is that I didn't push those connectors into the ECU well enough and the vibration caused one or both of the top two to work out just enough to cause a faulty contact, resulting in the car running (or not running) as it did. Of course, I'm just guessing. The Pettit ECU that I bought was from a forum member and he says it is good. I believe him. I think it was just my own incompetence and not fully inserting the plug that caused the problem.

Thanks for all the ideas today. I really thought the engine had blown. Turns out, it was a bit simpler.

 

Glad it turned out okay. Sometimes there aren't happy endings.

 

So (like a typical FD) she goes from a finicky bitch to a beautiful woman again....

 

i dont think we are going to let you do that

 

so did you put the petite ecu back in and make sure you hear the "clicks"?
I could tell this story would have a happy ending by the use of so much extra detail in the beginning of this last writeup, trying to build suspense for us, the whole time knowing the car was A ok.

 

Glad you got it home.
I know my fd would not let me give it more than a touch on the gas with out shooting massive backfires, i am talking automatic weapon fireballs and it would stall. Took out the spark plugs cleaned them and it was good to go.

But yea i would pick up a Power Fc and get someone to tune it you will be much happier.

 

You must have been dreaming about Io while installing the ecu!!!