stevedavies

Thanks for suggestion on MAF. I am going to look at it again this weekend. Will try and get more accurate timings for the intake holding pressure. I am not going to pull the intake unless I am convinced there is a significant leak. When I checked it it discharges from 1.5 to 0 in approx 15 secs. I am not sure if this is good or bad? My only reference is other RL threads which state the intake went from 2.5 to 0 in 4 minutes. Is mine bad or the other thread very very good?

stevedavies

For completeness I tried disconnecting the 02 sensor. No real difference to idle either with it connected or not.

stevedavies

Have taken the MAF & LH to be tested, need to start eliminating some of these systems

the flyin' scotsman

looking fwd to see your results...........good luck.

stevedavies

Malcolm... will do, MAF and LH will be with JDSPorsche tomorrow for test. Will post progress

stevedavies

So looks like LH ECU checks out ok. MAF is 4% out of calibration, is this worth rebuilding??

the flyin' scotsman

Did JDS advise that a MAF 4% out of cal. cause the idle issues?

I wouldn't think so.

Did you spray any cleaner under/along the intake to check for leaks?

John Speake

No, 4% is not going to affect the idle issue that Steve has. Unusually for the UK his car is a cat equipped car, so MAF ageing not so critical. However the aged MAF will afffect throitttle respons eas the LH goes open loop under those conditions.

3% aged is my advised limit for optimum drivablilty and power.

stevedavies

Decided to have MAF rebuilt with JDS, John is correct with his analysis, when i blip throttle engine hesitates a little then responds. We agreed the MAF probably isnt the cause of the problem, but i need to eliminate some of the variables. I ordered 'smoke matches' to help identify leaks. I stripped intake again to remove MAF so going to recheck all connections again. Going to remove throttle body from intake and apply some gasket sealant, retighten hoses etc. Also going to apply some flexible sealant to intake to engine gaskets (gaskets look real good quality so shouldnt need it). John is turning parts real quick so hope to get back in ther this weekend. Will report progress this weekend.

the flyin' scotsman

John........thx for the feedback. I don't recall when I bought my rebuilt MAF from you but it was a few seasons ago and was hopeful it would be still in calibration.

Steve...............so you've removed the intake again and found nothing very evident to cause the issue?

I also used all new intake gaskets and was very careful to torque all bolts per the WSM or many of the great write ups (my work was prior to Dwaynes write up).

Something else to chew on.............I essentially rebuilt the front end of a GT this spring and although the intake was off the owner decided not to rebuild the intake (ISV, injectors etc) and when the motor was back together it ran almost like our cars but worse. The owner then reversed his decision so we took the intake off again and replaced everything. I was very careful when putting the intake back on to ensure the gaskets were aligned by moving the intake around with new injectors fitted so all was aligned before torquing it down.
The car then purred like a kitten.

stevedavies

Malolm, Yes have intake back off ! I checked everything under there but everything was fine. I took off the throttle housing again and applied fine smear of flexible gasket compound to either side of 2 throttle housing gaskets. Also applied smear to underside of intake/engine gaskets. Waiting on the MAF on Saturday before tightening it down. Will be extra careful and ensure gasket is aligned ( using injectors) before tightening down. I have a good set up to enable me to pressurise the intake now so should be able to pinpoint leaks if any present. This is a challenge!

John Speake

Hi Malcolm, a rebuilt MAF should last as long as the original.

stevedavies

So replaced intake today with rebuilt MAF from JDS. Replaced the LH ECU which was checked out ok.
Idle is exacly the same at 1100rpm when warm. Checked vacuum at front damper and is 21 HG. Vacuum auxs isolated. Pressurised intake prior to starting, took over a minute to discharge. Tried smoke around intake when running and no leaks evident. I cannot think of aything else to check? I have checked replaced everything I can think of but it is the same high idle when warm. Tried discionnecting 02 sensor, made no difference. Throttle cable not snagged, I can hear TPS clicking and working.Tried creating vacuum leak by disconnecting golf tee isolating auxs , no difference to idle. The idle has not been affected by any of the intake work I did, suggesting it might be something else causing it??

The MAF rebuild has made a big difference to the response of the throttle ( as predicted John). The response is quicker and the hesistation is gone completely. Feels like a different car on the road.

Any suggestions what else this could be ?I am completlely out of ideas

the flyin' scotsman

what changed to give the longer pressure time? I believe you used the same gaskets but with some sealant? Regardless, I wonder if you plug the main vac feed to the dampers/regulator how that effects anything............also the vac lines to the air diverter and charcoal lines.

Can you borrow a LH from a good idling car?

Another thought, when you had the throttle body apart to replace the brgs was the throttle plate replaced in the correct orientation............theres a small 'cuttout' which should face the incoming air.

stevedavies

Malcolm, I just checked disconnecting various vac lines, the idle speed is independant of them all.
The vacuum is higher than previous at 21 HG, may be due to gasket sealant on throttle body and intake gaskets. Rechecked the throttle cable again, it is not snagged either

JDS checked out the LH as functional, I dont have access to another LH to compare either.