Hey guys, I haven't had much time to look into this problem, but I should be able to start looking into it pretty soon and wanted to see if anyone has any input on thing to look at that I haven't thought of.

First some info on the truck. MAF conversion using RJM injection overlay harness, Pro-M 70mm MAF, A9L EEC, and Tweecer R/T. 302 with GT40P heads, B303 cam, Typhoon upper/lower, MSD cap/rotor, MSD coil, Taylor 8mm plug wires, FRPP shorty headers, and also the EGR has been deleted using the RJM EGR plug and emissions has been disabled using the Tweecer.

Here's what's happening. Driving down the road and even sometimes sitting at idle, the engine dies like you flipped a light switch. Try to restart WITHOUT turning the key back off and it will not restart. Turn the key off, wait a couple seconds and crank it and 99.9% of the time it will start back up and run like nothing happened. When it dies, I check my gauges and have good fuel pressure, tach is still registering, but the air/fuel ratio is insanely rich at around 9:1. If you open the throttle (engine still off and key still on after engine died, transmission in gear, engine turning, but not firing), the air/fuel ratio will lean out and goes back rich when you close the throttle.

Every now and then it will do this, but catches itself before it dies. After it does this it runs rich (11.5-12:1 cruising and 12.5:1 idling) until I turn the key off and back on, then it leans out and runs normal.

I believe the problem to be with the EEC or in the ignition system somewhere, but I honestly don't know where I'm going to start yet. It certainly doesn't seem to have any spark when I try to restart it after it dies. Hopefully someone here has seen this before. If I need to, I could probably get out the GoPro and get some video of the problem too. LOL

 

***Bump***

 

Perhaps failing TFI module/coil or just a bad computer? These A9L computers are getting quite old, and they are susceptible to capacitor issues.

 

I bought the EEC new back in I think 2010, but it wasn't installed in the truck until late last year. So the EEC did sit for some time in my shop before it was used. The TFI module has never been changed though. It is the original module from 1994.

How would one go about diagnosing the TFI module?

 

How long have you been running the truck like this(no EGR and new EEC).

May be someone else can verify how the computer is adjusting to your

set up.

My recent trouble shooting experiences are exposing me to how

minute electrical differences can cause the PCM to not let

a vehicle run properly.

 

Hello my 91 would do the same thing. it took 3 years and alot of new words to find it. turned out it was the eec/pcm relay. When mine would stall it would only power the fuel pump. Every time i would start to look for the problem it would run great. I accidently bumped the relay one day and it quit so i took the top of the relay off and secured it i drove it several times before it did it. when it stalled left the key on and ckd the relay would only power up the the fuel pumps and no spark and extremly hot its worth a shot Walt

 

The truck has been running like this for about a year, which is only about 500 miles. The truck hasn't been driven much as it's been a project truck. It has had this problem since I got it running, it just hasn't been near the top of the priority list until now. All mods done to the truck were done at the same time, so the problem could lie anywhere. It was swapped from 4.9 to 5.0. While the engine was out it was rebuilt and fitted with the heads, cam, intake, etc. MAF swap and wiring modifications were made with the harness on the bench and all connections are soldered. The EEC connector was replaced b/c I broke some locks on the factory one. I got the new EEC connector from RJM Injection.

As far as the EGR delete goes, I do get a check engine light after I've been driving for awhile, but I haven't checked to see what the CEL is for. I think the CEL is EGR related. When the CEL comes on, the engine continues to run like normal. Nothing changes when the CEL comes on.

The only think standing in the way of me daily driving this truck at this point is this one problem. I has died on me once while trying to pull out on the highway and I had to turn the key off and back on to get it running. Scary to be sideways in the middle of a highway.

So, the first few things I will check out is the EEC relay, although I believe I have changed it already, TFI module, PIP, test wiring to EEC and grounds, and swap EEC. The sucky thing is that the problem is 100% random. I am unable to re-create the problem whenever I need it to. It just does it randomly whether it's idling at a stop light, cruising down the highway or pulling out on the highway.. It would be nice if I could make it do this and test after it does it.

EDIT: Just checked the price on TFI modules. I forgot there are two different TFI modules. Grey and black (push start and CCD). Does anyone know which TFI module the A9L should use? I have to make sure, but I believe the current TFI module is a grey one that was in the truck originally, so it originally powered a 4.9L 6 cylinder. LOL

 

Bump. Im out here working on this. Haven't found anything wrong with wiring yet. I have it sitting at idle right now, looking things over under the hood and touched the coil. It lit me up like a Christmas tree!!! Lol.

So if you just simply touch the coil, should it shock.you? If not, I have a problem here. Lol

 

The coil should not shock you.

 

I wouldn't think so. Lol. I will be getting a new coil I guess pretty soon and I'm going to try a new TFI module.

Can anyone verify that the grey TFI is the correct one for an A9L? Thats what my truck has in it right now.