Chevy 3.8 V-6 help?

[3.8L Strong]

I have installed a Chevy 3.8 V-6 into my 2002 PT Cruiser. The engine is out of a 98 Camaro. My problem appears to be at start up when the engine is cold. When I start up the engine when cold, it can hardly idle, and I can't even rev the engine up at all. When I try reving the engine to bring up the rpm, nothing happens. To overcome this condition, I have to continiously work the throttle plate manually trying to rev the engine a little bit at a time. After about 3 to 4 minutes of doing this I then begin to get better responses. When the response starts to get better, I usually try to get the rpm up to between 2 and 3 thousand rpm. When I'm finally able to get to that rpm, I'll usually hold it there for a few seconds until that rpm is steady and smooth. At that moment, it appears as if the PCM has then made an adjustment with the relearn process. After that happens, the engine is now able to idle on it's own, and I'm able to get some good rev's and able to bring the rpm up to higher levels. By this time the engine is getting warm and starts to run better. The longer I let it run, the better the response. However, if I shut down and let the engine get cold, and start it up again, the same things happens all over again. It's almost as if the PCM does not remember the relearn process it just went through. Just about everything is new. New spark plugs, new spark plug wires, new fuel injectors, new ignition control module and coils. New 02 sensors, new IAC valve, new EGR valve, new throttle body and all the sensors on it are new. The PCM is brand new. The engine is also a brand new rebuilt engine. The fuel pressure is at 50 psi which is well within the factory spec's. Any suggestions? If you prefer, you may email me at: Chevyone@hawaii.rr.com Thank you for your support, Tommy.

[RadRacer]

Re: Chevy 3.8 V-6 help?

hmmmm. Sounds like the timing may be off and it's running too lean. Make sure you have good gas in the car, then pull the PCM fuse. I believe you leave it pulled for 15minutes, and it'll reset everything. The car'll have to relearn everything so it'll run rough for abit, but it should eventually smooth out. Not guarantying this will work, just what I would try.

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

RadRacer, I forgot to mention that I'm getting two codes setting. One is a P0300 and the other is P1652. The P0300 relates to a multiple random misfire and the P1652 from what I found out relates to the Cooling fan relay 2 and 3 control circuit. Hope this helps! Tommy.

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

Today I started up the engine. I had to go through the same ritual again, this time I let it get hot to where the fan would kick in which is at around 195 degrees. I hooked up my scanner and got these readings:
DTC codes P0300 and P1652 were set.
P0300 relates to a Multiple Random Misfire
P1652 relates to the Fan 2 Relay Control Circuit
Engine coolant temp - 190
IAT - 124 deg F
IAC - 0 counts (I’ll explain why below)
Air Fuel Ratio - 14.3
Calc engine load - 5 %
Mass Air Flow - 10 g/s
02 Sensor Bank 1 Sensor 1 - 17 mv
02 Sensor Bank 1 Sensor 3 - 0 mv
02 Sensor Bank 2 Sensor 1 - 13 mv
EGR desired position - 0 %
EGR closed pintle valve - 0.75 volts
Spark Advance - 17 deg
Ing volts - 13.3 volts
Knock retard - 0.0 deg
Map volts - 1.1 volts
Map pressure - 12 inHg
Malfunction Ind Lamp - ON
Inj pulse width - 7.4 (it was fluctuating up and down)
Rich/Lean Status Bank 1 - Lean

Getting back to the IAC valve reading. This is the 3rd valve I have installed. It appears when the engine gets hot, the valve freezes up. When this happens, I get no response at the throttle plate. I can rotate the throttle plate manually and I’ll get no response from the engine. I’m not sure what is making the IAC valve get hot. Is it the wrong wiring configuration, or the heat from the intake manifold that is doing it? The engine does get up to around 200 degrees. I would think the IAC valve would be designed to work at that temperature. Is it possible that the IAC valve is causing the P0300 code to set? I would think so. I’m not too concerned about the P1652 code setting. I have just installed a new PCM and I think the Fan 2 Relay Control Circuit was not disabled. That is probably why that code is setting. I will check on that problem later. My main concern is the IAC valve and the P0300 code setting. Anyone experienced this type of heating problem with your IAC valve? Please review the data and let me know what does not look right. I know the IAC valve is one for sure, and the other would be the 02 sensors. Any suggestions? Thank you for your support, Tommy.

[auto666]

Re: Chevy 3.8 V-6 help?

vaccum is very low you could have a leak that could cause all your problems, except the fan relay

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

Which vacuum system are you referring too? Thank you, Tommy.

[auto666]

Re: Chevy 3.8 V-6 help?

the vacum in the intake manifolds created by the engine running
your stats say
Map pressure - 12 inHg
should be more like 18 not even race motors usually get thet low

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

Is it possible that the vacuum was leaking through the IAC valve? I could hear vacuum leaking in that area, however, I could not pin point the exact location, but it would surely explain why the engine is running the way it is. I'm going to remove the IAC valve and block off that port to see how the engine runs. I'll post the results when I'm done. Thank you, Tommy.

[3.4 slow to go]

Re: Chevy 3.8 V-6 help?

Is it possible that the vacuum was leaking through the IAC valve? I could hear vacuum leaking in that area, however, I could not pin point the exact location, but it would surely explain why the engine is running the way it is. I'm going to remove the IAC valve and block off that port to see how the engine runs. I'll post the results when I'm done. Thank you, Tommy.

not sure how it would affect them fangled new fullie cars, but an old carb trick to find vacuum leaks is to spray either water or carb cleaner in the area suspected of leaking & listen for a change in the running engine.

[CamaroRob97]

Re: Chevy 3.8 V-6 help?

You can still use carb cleaner to find leaks on fuel injection. I agree find were your losing your vaccum first.

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

I feel pretty confident that the vacuum is leaking through the IAC valve. I will be removing the IAC valve today. I decided to fabricate a mechanical IAC valve using parts from the existing IAC valve. Here's how it will work. I will remove the pintle valve from the IAC valve and use the pintle valve with additional springs for added spring tension to block the hole inside the intake manifold. I will then fabricate a cover plate with a hole in the center which will act as a guide and allow the pintle valve stem, to move in and out freely on it's own. The cover plate will cover the outer hole on the intake manifold and the springs will rest up against the inside face of the cover plate which will place constant spring tension against the pintle valve. My thought is with the correct spring tension, the pintle valve should move in and out on it's own. It should open slightly at start up, then close once the engine starts. Let's see how it works. If I could post pictures here, I would show you the results. If I can't post pictures then I'll post a link to where the finish product can be seen. I hope it works. Thank you, Tommy.

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

For those who would like to see how I fabricated my Mechanical IAC Valve you can click on these links. I have one picture posted at each link. So far it is working pretty good. I don't hear the vacuum leaking any more. The engine response appears to be a lot better, not perfect but much better. I may have to refine the spring tension. I installed one heavy duty spring. The tension is much stronger than the stock IAC spring tension. In anycase it appears to be working the way I thought it would. I'll keep you posted. Let me know what you think. Here are the links: Be patient, it may take a while for the pictures to post.

http://www.mypicshare.com/a6wk4tz5pic.html
http://www.mypicshare.com/ottsg9slpic.html

Update: I have modified the mechanical IAC valve even further to prevent any vacuum from leaking. The link to view the modification is listed below.

http://www.mypicshare.com/jpwj7m1spic.html

Thank you for looking.

[3.8L Strong]

Re: Chevy 3.8 V-6 help?

I'm still working on the mechanical iac valve trying to get the best possible setting which will allow the engine to run for further troubleshooting. What remains a mystery to me is why are my iac valves freezing up on me. As mentioned previously this is my third one that I have installed. It get's so hot when the engine is running that it then freezes up. When that happens, I'll have no response at the throttle plate. I can rotate the throttle plate but get no response from the engine at all. At that point it's so hot that you can't even touch it with your fingers. The way I look at it, it can only be one of two things that are causing this to happen. Either the intake manifold in the area where the iac mounts to is getting too hot, or there is a problem electrically with the wiring. Here's what I have planned. As soon as I can get the mechanical iac valve to work half way decent, I'll keep it installed, I will then hook up the original iac valve to the iac wire connector. I'll then place it on the side away from the engine heat, then start the engine and bring it up to the normal operating temperature. If the original iac valve still gets hot to a touch, then I'll know the wiring has something to do with it. If it doesn't get hot, then I'll know that the heat from the intake manifold is causing it to freeze up. Has anyone experienced this problem with their iac valve? Does anyone have any other suggestions as to how to find out what is causing this problem? Any help will be greatly appreciated. Note: For those who are reading this thread under the General Tech section, it has also been posted under the PCM & Sensors section. Thank you, Tommy.

[CDNFB]

Re: Chevy 3.8 V-6 help?

You definitely have a IAC wiring problem, but that should have no bearing on the non-responsive throttle plate.

First off, with your mechanical IAC closed with the engine running....well it won't run in that configuration anyway. With a full closed IAC with a closed throttle plate (or butterfly) there will not be enough air getting to the engine to sustain an idle. In this configuration, if your vaccum is actually as low as you stated, I would be inclinded to think that the valve timming (camshaft to crankshaft orientation) is off.

2nd, regardless of IAC valve position, when you open the throttle, the PCM should see the changes from throttle position sensor and the MAF and MAP sensors, thus adjusting timming and fuel delivery with a resulting increase in RPM. If your not getting the RPM increase, then one, some, or all of the sensors are not working properly. Since all are new, I would bet you have some major wiring issues.

[CDNFB]

Re: Chevy 3.8 V-6 help?

Hey, I was just in the Nitros section of this forum and there's a guy there who tapped into his TPS harness for the ZEX control box and now he has the RPM hang up on him with no throttle response. Symptoms are an awful lot like yours.

Check your Throttle Position Sensor and wiring.