I'm looking for some direction...?
My car is a '96 Vanden Plas with 122,000 miles.
I've had poor idle quality for some time now.
The car is not throwing any codes.
This started immediately after I cleaned the throttle body and...

What I've done:
1. Cleaned the TB, removed the IACV during the process.
2. Installed new TB boot, CPS, Fuel Pump, Spark Plugs, Coil Packs.
Immediately after the TB clean the car had a rough idle but ran fine. The TPS has not been touched and diagnosis with Fluke DVOM has
shown that the TPS is operating within spec.

3. The "AND" at the beginning of this year I installed a new audio head (Alpine) speakers and amplifier (Alpine. The new audio system was installed because at 17 years old the original was worn out, had poor sound quality and we (the Missus drives this car) want Bluetooth and IPOD capability. The intermittent stalling problem began after the audio system was installed.

Back to Number 1; when I removed the IACV I broke the heads off the two mounting screws. I drilled out the remnants of the screws and replaced with new. Yesterday I re-drilled and tapped for new screws - made a first class repair. Car ran fine but had a high idle. Idle speed was 2k RPM; if I "goosed" the accelerator the idle dropped to normal and then the car stalled and I couldn't keep it running.

Any ideas? Has replacement of the audio amp messed up the security controller and/or the ECU? "Re-orienting" the ECU is not possible as the local Jaguar dealer doesn't have a mid '90s PDU.
Could it be the IACV?
I have the workshop CD and will be researching the problem today.

Thanks, Roger

 

Roger,

It's possible that the ECU may need the idle speed reset via PDU. Whenever the TPS or IACV are disturbed or replaced. Not the answer you want to hear, I know. Was the idle speed ok before you did the TB cleaning? If so, this might be the scenario. Hopefully we will hear from a tech guru soon!

Did you double-check the installation and wiring for the new audio system? Shorts or grounds in the wrong places could cause all sorts of troubles, maybe even stalling, I suppose.

 

Hi Richard, thanks. I tend to agree with you re the PDU. Everything checks out electrically (Fluke DVOM) no codes and so forth.

The car popped a serious coolant leak under the intake manifold yesterday (more heartburn).

All of the hoses are new and the clamps checked tight. I can't see where the coolant is leaking from under the car so I started removing the intake manifold yesterday. The electrical harness is being a HUGE PIA to disconnect and move out of the way. Lack of access and one stuck connector...

I was very carefull about taping up loose wire ends during the stereo install, though anything can happen.

 

Roger,

Did you get that manifold off yet? Did you find that the bypass hose under it is split? I hear it is a real B*STARD to replace, unless you have the manifold off. Get that all taken care of, and we'll see how she runs then.

 

I pulled the manifold off Saturday. Not a bad job, just a lot of electrical connectors and coolant and vacuum lines. That BIG hose I changed about 20,000 miles ago. It looks like it moved, also the forward gasket on the water rail to block joint may be leaking (tell tale coolant in one small area). Everything will be cleaned, serviced, repaired, replaced. Classic Parts shows one knock sensor but I see two (forward and rear). The forward sensor is destroyed and will be replaced. The wire connection to the oil pressure guage sender had broken off the connector, that too will be repaired. I will adjust the ISCV and check the ECU connections in accordance with Jim Butterworth's directions. The starter motor acts up in hot weather and that will be replaced as well. There is absolutely no sign of oil contamination in the intake ports - at 122,000 plus miles! Impressive! IF this doesn't work I'll sell the car and get another.

 

I found part of my problem; I had a fairly serious coolant leak develop, actually I have had a nagging minor leak since I owned the car. Well now...I checked the water rail. Some ignorant SOB had been there before me. The four mounting screws were loose! I removed the rail and some dumb a$s in a hurry had removed it and rather than replace the gaskets had used RTV which didn't seal. Not only that he didn't have the common decency or take the time to remove the remnants of the original gaskets! Poor workmanship and cheap shortcuts like this is why I do my own work!

Undoubtedly Flat Rate at its finest!