Boost leak with no check engine?

[Furyian]

Okay let me start with saying that I have no check engine lights. I had a code 22, 51, and 34. I bought a new TPS and calibrated it. I replaced the coolant temperature sensor. All of my codes are gone now. My next question is concerning the code 34. Can you still have a boost leak and no check engine light? I ran the car to make boost and one of my intercooler pipes blew off. No big deal just put it back on tight.

My engine cranks fine and starts easily ... it has a hard time idling though. I think it may have a vacuum leak that causes the bad idle. I will replace the boost gauge that was installed in the car before I bought it since it only reads PSI and not vacuum and PSI. However, when I rev the engine to warm it up to try to get it to idle, it studders around 3k RPMs. Just to see I tried revving it past 3k and it was like it hit a rev limiter and same thing with you drive it. So could a boost leak be the problem with it not going over 3k RPMs?

I changed the spark plugs out not even 5 weeks ago.

 

[87n/a_supra]

yes you can have a boost leak with no check engine light. and as for the idle problem if you give it gas does it idle better, if so it indicates that your ISCV is eithe bad or going out.

 

[tbcmorris]

Check you afm per tsrm. It will cause a rough idle and a "rev limiter" at like 2800. Also its wiring is tied in with the tps. Check that its pluged in, the wiring is good, and then check the afm per tsrm.

 

[thevork]

Indeed check your AFM. One question arose to me: Did you check the timing yet and does the car run better when you change timing by turning the TPS ?

 

[Furyian]

When I fixed the TPS I really didn't notice a change in performance and even after fixing the coolant temperature sensor either. The only thing is that the temperature sensor fix made the engine a bit easier to crank. But if I sit there for a few minutes while the car gets to operating temperature it idles around 900-1000 RPMs so I have a hard time thinking it's a vacuum problem. Now when I make boost, it doesn't spool until almost 5K RPMs and it's only 5PSI [probably what the wastegate is set as since the owner before me never installed a boost sensor on the engine or a boost controller] But even then 5 PSI doesn't make the car feel like it's really performing.

Could the timing really effect that? When he set the timing the TPS wasn't calibrated and a lot of people say you can't set timing without that being set. Also I ran across a possible problem. Everytime I finish messing with the car, I remove the negative off of the battery. I'm going to see if its just the fact that the car has to relearn everything again.

As far as checking the AFM, everything is fine. So the AFM isn't the problem. Once the engine warms up I can rev without it hitting an imaginary rev limiter.

 

[thevork]

with warm idle @ 900-1000 rpm i'd be looking for a small vacuum leak if I were you. Maybe your bov? (that is, when you have an aftermarket bov)

Also, 5 psi @ WOT makes it look like a HUGE vacuum leak somewhere. So check the iC piping, especially the one that goes from your turbo to the IC. Remove it and inspect it.
It may be hard to spot as a tear in the silicone part of the piping may be closed @ idle but it can be a huge gap when driving the car.

If there is absolotely nothing wrong with the IC piping, check the wastegate. It may be stuck open.


edit:
If the ECU pulls timing you'll have less power indeed but the boost pressure should be higher. Also, don't drive it hard until you got a second opinion on your timing setting.

 

[Furyian]

I will put a timing light on it tonight just to be on the safe side. As far as the idling I noticed that my VSV is not hooked up. I was looking on the side of the throttle body and noticed that there was no vacuum line running off the bottom of it. Will this effect idle? As far as it running rich, I have a 440CC injector chip coming in for the FCON that came with the car so I will be able to lean it out a little bit with the GCC.

 

[thevork]

I will put a timing light on it tonight just to be on the safe side. As far as the idling I noticed that my VSV is not hooked up. I was looking on the side of the throttle body and noticed that there was no vacuum line running off the bottom of it. Will this effect idle? As far as it running rich, I have a 440CC injector chip coming in for the FCON that came with the car so I will be able to lean it out a little bit with the GCC.

There are two VSV's. The one closest to the firewall is used to operate the EGR. The one near the Nr.2 cilinder hooks up to your FPR (fuel pressure regulator) that is on top of your fuel rail. It makes sure that your fuel pressure is increased 1:1 with your boost/vacuum level. Please connect it ?

edit:
There you go, that's your vacuum leak.

 

[Furyian]

Well the only VSV I really noticed was the one near the firewall and the previous owner blocked off the EGR [I am in the process of trying to get the engine all back stock for the most part as far as EGR and boost sensors etc ...] I will check the other VSV. The other VSV is located above the intake manifold and the other side of the throttle body around the TPS? Whether it makes a difference or not there is also no lines ran to the BVSV either. [yeah I know I bought a half assed car but for the price it was worth it]

 

[thevork]

I think the picture below will explain everything to you.
At first it may look familliair as i took it from the cygnusx1 site, but I altered it myself to show how the vacuum routing should go when you remove the EGR and the Charcoal Canister.

Hope this helps...

 

[Furyian]

I appreciate the modified diagram greatly. I will definitely have to look into this. However what I thought was a VSV isn't I guess then. The item that I know isn't hooked up is the one that goes to a filter and it where the throttle stop is located. It seems like a diaphram of some sort.

 

[thevork]

You mean the thing that is in this picture? http://www.4cefed.com/browncar/tbstop.jpg

Anyway it will not solve the issues you talked about before.
Please check your IC piping thoroughly and check to see if your wastegate isn't stuck open.

 

[Furyian]

that's exactly what I was talking about ... So I will just plug it off. I will drive the car up on the ramps today and start checking the intercooler piping and see if I can get to the wastegate since its a external dump style wastegate. Any particular way you suggest checking the wastegate? Either way, you have been a great help especially with the vacuum hose picture because I couldn't find any diagrams with the EGR removed. And I want to complement the whole SupraMania community. The level of help, advise, and involvement is a lot better then the honda/acura communties that I was accustomed to. You guys [and girls] are awesome

 

[thevork]

That thing is called the VTV. It's some sort of filter for your dashpot. Don't take it off, it is supposed to go on to the thottle body.

Well I don't know how your turbo and WG are setup right now however it think makes sense that when there is no big vacuum leak and you're not building boost the next thing to check is your wastegate. Maybe someone can chime in and tell you how to check an external wastegate. I have no experience with that, i'm sorry.

btw I made that diagram myself and made it for a good friend of mine who also bought a supra and he wanted to know the vacuum routing with the egr and canister removed. It was never before published on a public forum. Don't know of anyone else making such a diagram but it would explain why you could'nt find much

And yes, this community is great and very helpful. Just wait, you'll be a supra expert in no time (There is always enough to repair/upgrade on a MKIII supra lol ) and can start helping others.

 

[Furyian]

I have composed a check list of things to check within the next couple days

• check coil packs
• check spark plugs and wires
• check intercooler piping
• check all vacuum lines
• run a compression check just for good measure
• check timing with timing light

Is there anything else anyone can think of that I might need to check?

 

[paradox616]

get a boost gauge with vaccume on it, find out if your problem is electronical or mechanical mate, once you know that then you can sort the issue out,

i had a leaky intake manifold gasket a while back, made it idle shit and blow smoke on boost,

 

[GrimJack]

Check your codes again, see if they've all gone away.

I'd suggest pressure testing the intake system to find boost leaks, it's WAY easier than pulling bits off to inspect using the Mk1 Eyeball. Smoke machine sure makes this easy...

 

[Furyian]

Honestly I never thought about using a smoke machine. I will definitely go that route with it.

The coil packs and spark plugs and wires were good. I still don't think it's a vacuum leak even though I will replace every hose. But once it warms up a bit it has excellent throttle response and idles 1K-900 RPMs. Even when I'm WOT in first gear it feels like a good build up to make boost but then boost doesn't register on the gauge until 5k RPMs and even at 5 PSI I should be able to feel a big difference when it makes boost. However, I will be hooking up the smoke machine to find some leaks *prays to find at least one leak* ... If I don't have at least one leak the only other option is to buy another wastegate.

And BTW I still have no trouble codes on the computer.

 

[GrimJack]

I'll say this: I have yet to check for boost leaks on a car and NOT find one. Well, except after I've fixed them all, of course.

I think EVERY Supra has at least a couple after 20 years on the road.

 

[Furyian]

Finally all ready to perform my boost leak test tomorrow [yay me get to work on the supra while everyone else is at parades due to it being Mardi Gras down here] ... I will be replacing all vacuum hoses as well but I got to thinking about something and need some info or feedback.

The car is a 86.5; the engine is a 89 7M-GTE with a 89 7M-GTE ECU but has 7M-GE cams in it [the previous owner's idea]. Would this have anything to do with my rough idle while engine is warming up or not so perfect performance in general?