On the way back from getting my car emissioned. (I passed but the gas cap was bad so I got to go back their and do it again I just replaced the thing 3 years ago too).

Anyways on the way back the car starts back firing on me it would idle kinda bad it would go from 600 to 900 searching for an idle I guess. Once I gave it gas it would "pop pop" and get no power out of it, just back fire. So I turned it off talked to my dad for a little while (he was following me just in case this kind of thing would happen) I went back started it and revved it a little, up to 3k and there was no back firing so I just went on trying to get home. After the 3rd time this happened I decided to have my dad tow it home and here I am safe and sound. One more thing at the emission place the car was idling just fine not jumping at all rock hard at 650 or around that.

I starting to think this car doesn't want to run but I'm not giving up on it I have put a lot of work in it. Last night it was a heater hose under the hood, now its this. What do you guys think it is. The distributor has about 175000 miles just like the car. The engine has about 80 miles on it. I know it probably has to do with timing, ESC, ESM, and the advance or something. Please help hopefully this will be the last thing and I can finally enjoy this car!

Runs good, gets hot, runs bad? Ignition module or coil? I also see that you have 80 miles on the rebuild? Flat tappet or roller?

Coil was replaced with the rebuild along with cap and rotor. As far as I know the ignition module is just as old as the distributor with 175000 miles. I heard that I could get that tested but I have never heard it from any one else but one thread from here. Can I get it tested? If it only fails when its hot I don't think they could see that its bad.

The engine is roller, kinda noisy for a roller engine too.

A thing that shocked me is when I was testing, the engine was about 160 by the time I was done testing it was about 220 I'm talking about temp by the way. On the way to the emissions place I kept it at 160 and it ran fine. on the way back it was 220 and it ran like crap.

I'd double check the plug wire that the emmissions place may have removed for their pick up lead. If the connector is turned inside the boot it might feel like its snapped on but is stuffed off to the side instead, which would kinda mess with that cylinder, miss firing occasionally. As far as it running like crap when it gets hot, my car is doing the same thing right now and I can't track the problem down. Luckily my electric fan has a manual switch and I just keep the temps down, that is till summer time temps really kick in.

They didn't take off any plug wires, all they did was open the hood and look to see if I had the equipment and close it. Took 2 hands to open and the 2 hands never left the hood. I have driven v8 as a v4 before and what happened today was nothing like that.

If it is the ignition module than I'm just going to get a reman distributor that comes with an ignition module

I wish I was data logging when this was happening then I might have a better idea of what happened.

Anyone else have any ideas on what it could be?

before replacing anything, something else to check is fuel pressure when its acting up. running too lean can cause a poor erratic idle, low/no power & a pop through the intake.

with the age on it, a new module wouldn't be a bad ideal.

The pump was frozen when I tried to start the new engine, so that has been replaced. I guess it could be the fuel filter because that sat for a while but that was replaced less than 100 miles before the engine went

When it back fired I heard it to the back of me like through the tail pipes I guess its not really a back fire then...

I don't know if this is related to this problem I was having 10 miles ago where it would die and not start for 30 or so mins. But when that was happening I checked the fuel pressure and it was just fine it had about 40 PSI to the rail

When I was putting the distributor back in it looked like crap it deffently showed miles on it I think I might replace that just because of its age. About how long do distributors last and its ignition module?

I tested the ICM today. I didn't get much time over the weekend to work on it. Anyways the ICM was ok. the cap and rotor looked good too.

I hooked up the car to my laptop and I was looking at the MAF grams. I noticed it would jump to 32 grams for a split second... I haven't learned what is normal yet but with the engine off the MAF reads 5 grams and it jumps to 32 for a split second with the engine off it's so fast if you blink you'll miss it. I don't if thats just interference or an error but I thought I would see what you guys think of it.

If its nothing next I'm going to heat up my ECM and tap on it to see if it messes up the engine idle. I don't wanna hurt my new engine so I'm checking things that I don't have to check when it happens but if I don't find anything wrong that's what I'll have to do.

If that engine back fired hard, that could certainly damage the MAF sensor. It should hold steady with the engine off. Unfortunatly this may be one of those deals where one problem led to another problem.

How did you test the ICM? Unless you tested it at 200 degrees or so, the test is useless. Ive seen lots of bad ICMs test good on a tester. I wouldnt heat up the ecm. Nor would I knock around on it. This is an outside ECM issue, more than likely. I would check fuel pressure now, while its acting up.

Oh I loved this fun problem. About this time last year I experienced the joy of replacing my fuel pump. I got to drive it for 3 weeks after that before I had the backfire/no power thing you've got.

Long, long story and a couple weeks later, I figured out it was my ICM. I had recently rebuilt my stock distributor and used the wrong kind of lube under the ICM (I used silicone tune-up grease, not the heat sink stuff that came with the ICM). DOH!

Anywho, the guy who said testing a room temperature ICM will prove nothing is right. It needs to be hot. It's not an expensive part to replace and really isn't that difficult to do. Spend a few dollars and an hour and at least eliminate the ICM as a potential problem. If it's 175,000 miles old, I think it's time might have come.

Eric

K I'll replace the ICM. Would it be a good idea to replace the distributor with it?

I just let the ECM heat its self up and gave it a few hard taps and nothing happened just like it should. In my last firebird I had the ECM fall out once and hit the car floor real hard when I was racing it, nothing happened and car kept going. These ECMs should be able to take a small amount of beating. If they don't then every pot hole we hit would mess it up.

I want you guys to look at this data log I recorded its real short but it shows the MAF jumping to 30 pause it right at 197 and you'll see 30 grams for the MAF. This is with the engine off I was getting it set up so I can data log the problem if it were to happen. This is in turnerpro rt with 165_6E.ADS

I'm not real good with datalogs or MAF grams, so I can't give you any input there.

As far as replacing your distributor too, you needn't spend money where you don't have to. You could always "rebuild" what you have if you want to. I did that, which meant new ICM, pickup coil, and a thorough cleaning (use heat sink grease!!) I think a rebuilt stock distrib works just fine. That said, if yours isn't giving you any trouble, leave well enough alone!

Eric

If i was you i would get a new distributor module and replace that before you do anything else. The way you are discribing what the car is doing and with that many miles on the module it is a very good chance thats what it is. That would really be the only reason it would carry on only when it get's hot. Mostly everything else on a car works or it doesn't. Make sure when you put the new module in to put dielectric grease on the underside, this could make it break up too.

hehe I'll be sure to put the right kind of grease on it. I hope it comes with it because if it doesn't I would have never known to put it on with out you guys telling me.

I'll post my 30 MAF grams question in the DFI and ECM forum.

I hope it fixes it thanks for all the help!

JP82- an ICM is an ignition control module (aka distributor module).

This sounds similar to a problem that I'm experiencing. Did your car ever shut off from this?
I have a brand new 350 crate motor and I went to drag my car and it was running hot (230) by the time I got up to the line, I left hard off the line in 1st, I heard some loud backfiring, and next thing I know my car was off. I couldn't restart it at all. Let it sit for 20mins with the hood up and it started right up and drove fine. Any ideas if this could be the ICM?

On one hand I'd like to say yes the ignition failed due to heat sink, on the other hand it seems as if if reverted to a lean setting that the motor couldn't handle. Since you swapped out the motor for a 350 I can't say for sure that the problem isn't related to the distributor.Are you still using the original CCQ-Jet and HEI 7-Pin distributor or something else.

My car shuts off for long periods of time like that too. However, it has never backfired before shutting off till recently. The third time it started back firing I turned it off and it wouldn't start again. 15 mins later when I got it home I started it and sounded just fine. the shutting off problem was not a warmed up type of problem. It did that to me when the engine was at 120 or so, I put gas in it, went to start it and it didn't start till I tried again 30 mins later.

I don't know if I have fixed the problem however. I replaced the ICM and trimmed down the spark wire boots on the distributor side a little. Started the car and I noticed it returns to idle after reving it faster then it did before. I don't know if replacing the ICM would do that?? I'm going to test drive it when someone has time to tow me home in case it breaks down again.

How old/miles is your distributor, coil, ICM?

I was still using the ccqjet and the hei distributor, however my car is currently at a performance shop and I swapped the carb for a holley non computerized and a different distributor that also doesn't plug into the computer anymore.

Also I replaced my fuel pump with a holley mechanical on the motor and the mechanic just told me today that I had the wrong line hooked up to the pump, I had the one that feeds the gas plugged cause a few guys told me it was the return line
I got a custom fan switch installed also so I won't be running that hot (235) anymore