Overboost or faulty guage?

[jimmythesaint]

My boost guage is pegging on acceleration, the needle sits at .5 bar at cruising speeds and at .2 bar at idle. I've been to 1.25 bar of boost in another Esprit and this certainly doesn't feel like that much.

Anyone else experience this or have any suggestions? I'd hate to nuke my motor if it's accurate...

Thanks.

[Autocross7]

Sounds like your waste gate may be faulty? I have seen a faulty waste gate cause some interesting boost guage reads and the power goes away even though the motor seems to rev out okay.

Drive topless!!!
Cameron

[jk1]

check the vacuum lines at the boost solenoid, turbo and wastegate.

Has this been going on for a while or did it happen all of a sudden?

[jimmythesaint]

I just got the car so I don't know how long it's been an issue. I'll check the vacuum lines tonight when I can.

In the interim, do you think it's safe to drive? The overboost fuel cutoff isn't intervening and it runs fine.

[autocross7]

Should be okay to drive, just down on power. I did not see what year your Esprit is, but if it is a 4 pot car, it has an air pump for sure... if there is a vacuum leak, you may be able to hear the vacuum pump running.


Drive topless!!!

[jimmythesaint]

Mine's a 95.

I looked and the overboost sending unit this morning and it was hooked up fine (but it was idling at .5 bar!).

Anyway, coming home tonight the needle jumped up and down a couple of times then started working properly with no difference in performance. So I'm guessing it's a vacuum leak or an electrical gremlin somehwere.

Thanks for the advice guys.

>> Edited by jimmythesaint on Thursday 25th May 09:00

[jk1]

autocross7 said:

I did not see what year your Esprit is, but if it is a 4 pot car, it has an air pump for sure... if there is a vacuum leak, you may be able to hear the vacuum pump running. Drive topless!!!

You are correct about vacuum leaks but the boost control is not part of the vacuum system. I incorrectly stated "vacuum lines" in my previous post but they are actually pressure lines...

There should be a diagram of the vacuum and boost pressure lines/solenoids on the underside of the boot lid. Check it and make sure everything is as it should be. Could be a bad gauge but split or incorrectly attached pressure lines or bad solenoid can cause the problem you describe.

If you have a manual pressure gauge you could hook it up to the rear of the intake plenum to see if it's actually measuring .5 bar at idle. There is a pressure line that comes off a plastic fitting at the rear of the plenum and goes through the right engine bay sidewall to the boost gauge transducer. Disconnect it and plug in a gauge to see what the actual boost pressure is.

Cheers,
Jim

[JimmyTheSaint]

Is it even possible to make .75 bar of boost @ 900 rpm - or 1.25 @ 1500rpm?

My guess is no, even with a faulty wastegate. Just thought I'd ask as I am paranoid and puttering around like a little old lady in a buick listening for any noises that might indicate trouble. I'm going to try and sort it out tonight, but I thought I'd see what the consensus was before I have it towed home.

One minute the guage is working fine, the next; crazy town...

[jk1]

Well that's a lot more radical than what you first described. That's one helluva turbo you got there.

Sounds more like a bad gauge or transducer. I'd still check it if you have access to a manual pressure gauge just to be sure.

[JimmyTheSaint]

Yeah, it's crazy. The guage is all over the place but I don't notice any difference in performance.

Thanks for the tips.