First, the details of my car: it's a 1985 Camaro with a fully rebuilt 383. Edelbrock RPM heads, Holley Stealth Ram MPFI, MSD distributor & coil, mild Comp cam. The computer and wiring harness have been updated to the speed density system out of a '90 Camaro. Basically everything is brand new - new Walbro fuel pump, new 30 lb. injectors, new plugs, wires, distributor, etc. I also went through the chip burning-data logging-re-burning process three times, to the point that the vendor says the chip is "perfect".

Now, what I've checked (multiple times): valve adjustment, timing, fuel pressure, TPS voltage, spark plug wires, no vacuum leaks, no spark jumping.

The problem: The car idles just find, right around 950/1000 RPM. No evidence of a miss or backfire or anything of that nature. If you rev it up quickly, it sounds great, RPM's rise steadily & come back down normally.

If you take it for a ride, however, there is an issue. When you are at a stop & step on the gas, the car falls on its face. It just bogs down & stutters for a few seconds, then eventually goes. It sounds almost like a miss at that point, but eventually smooths out and the car goes. Then, if you are moving along at cruising speed and give it a little gas (like you are trying to maintain a set speed), the RPM's will jump up 300-400 & then drop back down, you can both hear & feel this as well as watch it on the tach. It seems that the higher the RPM, the less noticeable the issue is.

Some other information: my engine builder originally screwed up, didn't have the timing marks lined up correctly so I had a hell of a time getting this thing started at first - I have no faith that the rest of the engine is correctly put together so nothing is off the table in terms of possible causes.

I noticed the other day that the electrode that comes out of the coil is very loose, you can spin it around with your fingers. I know this isn't normal, but not sure if that could be causing my issue? I've also read that perhaps the PCV valve could be bad or the wrong one, acting like an intermittent vacuum leak. Other than that, not sure what else to check or what to look for? All of the data I have on the TPS tells me that it's working fine, but at the same time a lot of the research I've done points to perhaps that being bad.

Any advice/information on this is greatly appreciated. Alternatively, if there is a recommended shop in the metro Detroit, Michigan area I'm not opposed to taking the car there & getting it checked out. Thanks in advance.

 

Well you touched on ignition and timing. You may want to verify fuel pressure too. Seeing how this only occurs under a load (pulling away from stop) it could any of the three. Where is your timing set @ base and full advance? Do you have a box? Try the basics one more time and see what happens.

 

what style and heat range plugs are you running? i had a similar issue with my car, loading up at idle. my tune is just a bench tune and is rich. i went one heat range hotter on the plugs and took care of the hesitation and stutter. when its not fully warmed up, it will surge at highway speed, but goes away once it reaches 175*. for how cheap they are, replace the cap, rotor, and pcv to ensure theyre in good order

 

The base timing is, I think 8 degrees. Sorry for being a noob, but I'm not sure what full advanced timing is or how to check - isn't that computer controlled?

When I first started the car up, I had the plugs recommended by Edelbrock - Champion RC12YC. But I changed them out for NGK BK5RE, which are in there now. I've had the same problem with both.

No ignition box on the car.

This is somewhat strange. On Friday, I installed a underhood fuel pressure gauge. When I did, I had to remove the upper intake. When I did, the gaskets ripped but I didn't have replacements. So, I put the gauge in, put the upper intake back on with the ripped gaskets and installed a replacement coil (see above). When done, I drove the car and the problem was, for the most part, gone. Still didn't run 100% the way I would expect but it was greatly improved. I thought the old coil was bad & causing my problems. On Saturday, the new upper intake gaskets arrived so I took off the upper, cleaned everything & installed the new gaskets. When done, I took the car for a ride...and the problem was back, maybe worse than before. So apparently, it was a coincidence that it was fine before, or I fixed the problem and re-broke something. I have no idea. Forgive me if this is stupid, but I was wondering...is it possible that the car isn't getting enough air (I have the stock dual filter setup, nothing special for intake air) and when I ripped the gaskets & put it back together, it allowed more air in & helped the problem?

I have also noticed that the problem is way worse when first starting the car. My first few take-offs are rough, but as the car warms up the problem gets better. It doesn't go away, but doesn't cause nearly the issues.

Finally, when I had the upper intake off, I noticed that there was a small amount of oil in there - the PCV valve also had a little oil in it, as did the hose. Is this normal?

 

You are correct in that the timing is CPU controlled. I asked as it appears you have a different dist. Unless its just an msd cap. That kind of stuff worries me unless I know it is correctly installed. If you have been playing with the manifold a vacuum leak is a possibility. Air filter won't have much to do with it....unless it were clogged so:

Verify all wires are connected and in correct order
Rule out vacuum leak.
Verify fuel delivery as required for your motor (i don't know specs do mpsi)
Verify Tps, as well as all other air meter/flow sensors.
Verify coolant temp sensors.
Verify base timing and CPU ability to retard,if base is 8, it can retard to 0 easy.
Verify cat is not plugged
Verify knock sensors there/ functions.
Verify emission related sensors that control CPU inputs function. Ex o2
Check codes and verify you can at least get a read....

 

Thank you for all of the information/suggestions.

I have been through almost every item on that list. All sensors are new and reading correctly, both according to my datalog as well as my brother's shop scanner. Firing order fine, no vacuum leak, no cat to get plugged, etc.

Yes, I have a full MSD distributor. When I built the engine, I went to the HSR which requires a small cap distributor & externally mounted coil.

I've been focusing on fuel. I checked my pressure again, I think it's too low. At idle with the vacuum hooked up (I have a Holley adjustable regulator), it was only at 39 lbs. or so, at higher RPM it would drop to 35-36. I adjusted it yesterday so that with the vacuum line unhooked, I'm at 45 PSI and with it hooked up it's at 41/42. Didn't get a chance to drive it yet, hopefully I can do that tonight.

 

Okay, I think I ruled out fuel pressure. I've been playing around with, taking it up and down and all around and while I can get the car (generally) to run better or worse, my issues are still there. I set it where it seemed to run best (44 psi, I think) and then moved on to other things. Not sure what any of this means, though.

First, I checked the vacuum. At idle, it has 15 in. Bounces a little between 14-16 but nothing major. At higher RPM, it's nice and steady at right around 17 PSI.

My timing, on the other hand...no idea what to make of this, I just don't enough about timing to know if this is normal. Back when I set it when the engine was first installed, I started the car, disconnected the timing plug (remember, this is the wiring harness & ECM out of a 1990) and set the timing to 8. Plugged the timing connector back in and away I went - I wasn't smart enough to check the timing after that.

So today, I check the timing with the connector plugged in - it's at 28. I disconnected the plug and checked it, it's between 9 or 10. Plugged the connector back in, it stayed at 9 or 10 and my engine light was on. Shut the car off & restarted, light was off and timing was back to 28. I then held the idle up and checked it, I don't know exactly what RPM I was at because I was doing this by myself from under the hood but I kept creeping higher and higher until the timing stopped changing. Based on the sound, I'm guessing I was around 3,000 or 3,500 RPM. Anyway, at that point my timing was at 52 or 53. Is this normal?

One more question, going back to my hesitation. I was paying more attention today and noticed that my two issues may be two separate things (or one thing causing two different symptoms). The two symptoms:

1) When pulling away from a dead stop slowly and the car bogs down/hesitates, the tach doesn't move - if I'm at 2,000 RPM, the car will start to sputter and jump a little but the tach stays right at 2,000 RPM. Does this point to anything?

2) While driving, if I'm going 35 or whatever and give it just a little gas to maintain speed, the RPM will start to jump up and down, like from 1,400 to 1,700 then back to 1,400, back to 1,700, etc. You can hear and feel this, too. When this happens, if you give it more gas it immediately goes and the jumping goes away.

 

No a full advance timing of 52 is not normal. I do not have CPU timing mind you, but I am @18 at base and 35 at full advance which is 850 rpm idle and 3000 rpm for full advance. I can understand if your base is 8 and you advance to 20+, but 52 I'm pretty sure isn't even possible. I'm starting to wonder if you have some type of CPU issue. What codes have you pulled?

 

CPU codes? None, there are no codes present.