Help Me Troubleshoot

[jasontiff]

Over the past 2 weeks a friend and I added a bunch of stuff to the car. Since it may be relevant, here are the mods:

• Gen. II intake manifold w/Gen. II injectors
• timing set
• new serpentine belt
• ported heads
• new plugs
• new O2 sensors
• headers
• pushrods
• 708 cam
• 1.7 roller rockers
• water pump
• gaskets all around

For the first 2 days, the car ran fine. I didn't flog it (kept it under 3k) because I still needed to break it in. Yesterday, I heard a clanging and chased down a pushrod that had come off the rocker arm. I put it back together and now it wants to stall when it gets no throttle.

To get to the rocker arm I had to pull the valve cover and subsequent hardware (idle air controller, PCV valve, throttle cable bracket, etc.) but it's all back on there. I made quite a mess down the driver's side with oil when I ran the engine for a few seconds trying to find the loose rocker, and I'm wondering if some oil got into an electrical connection.

The diagnostic software I have is being an ****, otherwise I would have seen if the car is throwing any codes. Any ideas?

 

[dave6666]

TB linkage synchronized - both TB's opening?

It wants to stall when it get NO throttle (IAC bad?), or ON throttle?

What about that "diagnostic software"? What is that? Your PCM or some laptop or?

Otherwise, never heard of an "oil short."

Could it have gone into a fail safe or limp mode?

 

[jasontiff]

TB linkage synchronized - both TB's opening?

It wants to stall when it get NO throttle (IAC bad?), or ON throttle?

What about that "diagnostic software"? What is that? Your PCM or some laptop or?

Otherwise, never heard of an "oil short."

Could it have gone into a fail safe or limp mode?

We sync'd the throttle bodies when we put it all back together. Would unbolting the throttle cable mount on the passenger side of the intake throw that off again?

It wants to stall when it gets no throttle. As soon as my foot is off the gas the RPMs fall below idle shortly before the engine sputters and stops.

I bought an EASE diagnostic module from Roe last year. It's OBDI and plugs into the serial port of a my laptop and into a diagnostic port that is wired into my VEC. You have to jump through hoops to get it to start and when it finally connects, it stays for 5 seconds then says the connection fails (before logging any trouble codes).

Is there a way to get it out of the limp mode (unless this is a clever way to say my equipment ain't functioning )? I'll check the connection on the IAC since that was disconnected to pull off that valve cover.

 

[dave6666]

I don't even know if the stock PCM has a fail safe or limp mode. I think the VEC does and some factory PCMs do, but had to ask.

Why not call Roe on your software issue?

And yes, check your IAC. If that no workie then no idle either!

Dunno how the linkage works so on your own there...

But how about that pushrod coming loose? Is that common? What if it happens when you aren't being casual on the gas?

 

[BOTTLEFED]

Did you replace the lifters when you put the new cam in?
It may not have anything to do with your problem, but since they wear in together, the cam and lifters are usually replaced together. If you have a bad lifter the pushrod will just keep popping off.

Did you follow the proper instructions for adjusting the rockers?
How is your oil pressure?

 

[BOTTLEFED]

And yes, check your IAC. If that no workie then no idle either!

This is true if you cannot get it to idle, but it sounds like your problem is only when you are driving and let off the throttle. This is a totally different situation.

 

[GR8_ASP]

Sounds like the throttle synch issue. Taking off one of the cable brackets could change the adjustment.

 

[Martin]

It could also just be the PCM acting funny. I've had that exact same thing happen for no reason, and sometimes when the battery has gone dead. I *think* you can reset the pcm by touching the positive and negative battery terminals together (obviously disconnect them from the battery...). Or, just give it some gas for a while - it will probably re-learn what it is supposed to do.

 

[jasontiff]

Did you replace the lifters when you put the new cam in?
It may not have anything to do with your problem, but since they wear in together, the cam and lifters are usually replaced together. If you have a bad lifter the pushrod will just keep popping off.

Did you follow the proper instructions for adjusting the rockers?
How is your oil pressure?

I bought new lifters to go with the cam.

I tightened the locknuts until the pushrods would no longer spin, backed 'em off until I could barely turn them, then locked the nut down.

I always let oil pressure build up before I let the car move, so that was fine. Once the car started acting up I didn't glance back down...maybe I lost pressure at some point. I'll look again tonight.

 

[jasontiff]

This is true if you cannot get it to idle, but it sounds like your problem is only when you are driving and let off the throttle. This is a totally different situation.

I had both actually. When sitting and idling it'd stall, and it'd do the same when I let off.

 

[jasontiff]

Sounds like the throttle synch issue. Taking off one of the cable brackets could change the adjustment.

Well, that's a relief. It sounds like either the IAC or the throttle cable, both of which are easy fixes. I assumed it was something I took off to remove the valve cover but didn't know if the problems I was experiencing lent themselves to it.

Now that you mention it, the cam is a lot lumpier but when I was driving last night it seemed like the 2 banks were off. I went to a car wash to get some of the oil off the motor and when I pulled into the bay the sides didn't seem sync'd up; like they each had their own agenda. I'll definitely check that tonight.

Thanks for all of the input...if anyone else has any other ideas let me know. I'll post up tonight once it's resolved.

 

[TexasPettey]

The throttle cable on a Gen1 does not affect the idle, except to increase it. There is an idle adjustment screw on the TB's. When the car goes to idle, the flaps are at rest on that screw. If you used the same TB's as were on the car before the mods, I would not suspect the TB's adjustment for an idle issue. I would expect that unless the screw had moved the 'close' position on the flap, a TB adjustment issue would only cause the car to idle higher.

If you suspect the IAC, you can manually adjust the screws to open the flaps a small bit. That has the same effect as the IAC opening up. I know, because I had to mess around with my idle adjustment screw quite a bit on my Accufab TB's to get it right (not too high or too low).

There is a learning period with the computer if there have been mods, especially a CAM. During that period, it's very likely that the car will stall coming off RPM and will not idle. I had this in spades with my ROE the first time the computer did the learning.

Did you see this effect when it first came alive after the mods? If not, and you didn't kill power to the PCM, I would suspect that is not the issue either.

If the engine bay is a mess, you can clean out the oil with a couple of cans of starter fluid. Just spray it all over the covered areas of the engine bay. It will push all the junk onto the floor and will evaporate cleanly & quickly. Just don't get it on your exterior paint.

Is your VEC mounted on the driver or pass side? If it's on the driver and you were working on the driver side, you may have loosened some of the connectors. I'd check those.

 

[TexasPettey]

It could also just be the PCM acting funny. I've had that exact same thing happen for no reason, and sometimes when the battery has gone dead. I *think* you can reset the pcm by touching the positive and negative battery terminals together (obviously disconnect them from the battery...). Or, just give it some gas for a while - it will probably re-learn what it is supposed to do.

That is a good suggestion. If something happened that screwed up it's learning, then it needs to go through the process again.

 

[jasontiff]

That is a good suggestion. If something happened that screwed up it's learning, then it needs to go through the process again.

I'll check it out too. I'll give the other items a whirl first because it'd be coincidental if the PCM started acting up at the same time I unbolted all that other hardware. But I think with these 3 suggestions I'll be up for the drive tomorrow.

Dave/Chris, you guys coming out tomorrow?

 

[dave6666]

Planning on it.

 

[jasontiff]

The front splitter gonna be on? I've seen the side splitters and the rear diffuser; they're old news now . I guess I could marvel at the brakes and/or wheels, but I want to be pushy and say "BRING ON THE FRONT SPLITTER"!

 

[dave6666]

Front splitter will not be on. I have been screwing off and working s l o w l y.

I don't think you can control whether or not you marvel at the new wheels and brakes.

It's not up to you; a force you cannot control

 

[Tom F&L GoR]

I can verify that simply removing my IAC, installing one I wanted to test (it was a dead one) and reinstalling my good one produced the same idle-stall problem you describe. It took 4-5 trips over two days for it to relearn. Thought I had screwed myself. I kind of remember that having the AC on was supposed to help, can't say if it did, though. Miracles happen and it got smart again.

 

[Martin]

I can verify that simply removing my IAC, installing one I wanted to test (it was a dead one) and reinstalling my good one produced the same idle-stall problem you describe. It took 4-5 trips over two days for it to relearn. Thought I had screwed myself. I kind of remember that having the AC on was supposed to help, can't say if it did, though. Miracles happen and it got smart again.

Same here - I thought something was really wrong the first time it happened. It did re-learn, though. After it happened a few times, I took it in stride. Someone told me at one point to disconnect the battery and hold the positive and negative terminals together for five seconds, and when I reconnected the terminals it started right up with no problems. Not sure if it was just a coincidence or good advice, but it seemed to work...

 

[jasontiff]

I don't have an IAC to replace it with, but I can double-check the connection and the throttle cables. I think with the collective knowledge of the board we've isolated the problem.

It's odd, though; after doing ALL those mods over 2 weeks, it started right up and idled fine with no tune. I disconnected the IAC for about an hour and it flips out? Damn car.

 

[Tom F&L GoR]

Try it on Dave6666's car when he comes over this weekend. Just disconnect and reconnect. It'll be fine, Dave. Eventually.

 

[Martin]

I don't have an IAC to replace it with, but I can double-check the connection and the throttle cables. I think with the collective knowledge of the board we've isolated the problem.

It's odd, though; after doing ALL those mods over 2 weeks, it started right up and idled fine with no tune. I disconnected the IAC for about an hour and it flips out? Damn car.

In my previous life I was a controls engineer and desiged the control logic and scheduling maps for all kinds of things somewhat related to the PCM in these cars. All it takes is one parameter to go outside of the map range and crazy things can happen with the logic. When it's in a Viper, it's an annoyance. When it's on a AH-64 engine controller, it's a big problem...

 

[Tom F&L GoR]

In my previous life I was a controls engineer and desiged the control logic and scheduling maps for all kinds of things somewhat related to the PCM in these cars. All it takes is one parameter to go outside of the map range and crazy things can happen with the logic. When it's in a Viper, it's an annoyance. When it's on a AH-64 engine controller, it's a big problem...

So, what, do they just hover around for a while until it learns? Dave, you need to pay attention here.

 

[Martin]

So, what, do they just hover around for a while until it learns? Dave, you need to pay attention here.

It depends on your definition of 'hover' and your definition of 'a while'. We worked on one problem where a certain parameter went outside of it's map, and that caused each engine to go into a death fight with the other one. Since they are shaft-connected to each other, it was a bad thing and led to a lot of emergency 'landings'.

 

[TexasPettey]

Dave/Chris, you guys coming out tomorrow?

I'm hoping to, but I'll have to have the kids in tow with the truck vs the Viper. I really want to check out your car. I think it's awsome that you took on the heads/cam effort yourself.

 

[99 R/T 10]

I don't have an IAC to replace it with, but I can double-check the connection and the throttle cables. I think with the collective knowledge of the board we've isolated the problem.

It's odd, though; after doing ALL those mods over 2 weeks, it started right up and idled fine with no tune. I disconnected the IAC for about an hour and it flips out? Damn car.

Is the IAC the same on the Gen I as it is on the Gen II? Never heard of anybody putting a Gen II manifold on a Gen I engine......................................

 

[99 R/T 10]

It depends on your definition of 'hover' and your definition of 'a while'. We worked on one problem where a certain parameter went outside of it's map, and that caused each engine to go into a death fight with the other one. Since they are shaft-connected to each other, it was a bad thing and led to a lot of emergency 'landings'.

Did the Apache experience a Dual engine rollback?

 

[Martin]

Did the Apache experience a Dual engine rollback?

That was basically it - the fuel management system was throttling back each engine until the pilot had to autorotate down. Since the engines are connected, there is a load-balancing system. The system would get into a situation where the controller was trying to load-balance the engines, and certain things would occassionally cause the fuel management system to throttle back on one engine, then the other engine would throttle back to balance the load, etc.

 

[99 R/T 10]

Yeah, the Blackhawk had a couple too. One even landed on I-25 up in CO about 12 years ago.

 

[Martin]

Yeah, the Blackhawk had a couple too. One even landed on I-25 up in CO about 12 years ago.

The UH-60 was infamous for the problem - they released all kinds of warnings to Blackhawk drivers. It generally wasn't as pronounced and unrecoverable as the AH-64 problem - the UH-60 would experience a 10-20% power drop, but if the pilot hung in there, dropped collective and nose down a bit to keep rotor speed up, it would sort itself out after a few seconds. There were a few emergency autorotations because the pilot would start adding collective to arrest the descent, and that just dropped the rotor speed so far down that the engine couldn't recover.

If memory serves me correctly, the problem with the AH-64 was a set of wires from various sensors that chaffed. One of the sensor wires would ground out against the frame, sending an out-of-map voltage signal to the controller, and that would start the cycle, and it wasn't as easily recovered from as with the Blackhawk...

You're right - it all happened about ten years ago. Seems like yesterday