Boost Problem? '90 SE

[onthetrack01]

I just purchased a 1990 SE with 25,000 miles. I just had the full C service completed and the tech documented the car in great condition.

When back from the shop, I had driven the car less than 20 miles, during which it worked perfectly, and then all of a sudden the car would not boost. In fact the car will not exceed 3000RPM in any gear, and then would eventually not spin enough RPM to maintain idle - and dies (this despite flooring it). When I started it up again, it ran again until 3000RPM, then would not boost and will not exceed 30000RPM.

Bad turbo, fuel pickup? Any ideas?

[cnh1990]

If it felt like fuel starvation right after when the turbo engaged. It may be a problem with the small hose connection to the turbo waste gate. It has a habit of coming off. If that happens the turbo will over boost and the management computer will shut off the fuel flow to protect the engine.

[onthetrack01]

Thanks for your reply! Today, I took it out again to see if the problem would occur again. This time, the car would boost up to 0.5 bar and then cut out, not allowing the car to pass 4,000 RPM. Could this be the same issue you just described? Why would the car not rev above 4,000 RPM (today, 3,000 RPM yesterday) if the boost was the issue? Wouldn't the car just not boost but permit the usage of the full rev range? And why no boost, stop at 3,000 RPM yesterday, car stalls after 10 minutes of use, and then max of 0.5 bar boost and max of 4,000 today?

Thanks again for the reply!

[cnh1990]

Okay another problem may be the cat preheater flap in the exhaust pipe, sometimes this gets stuck and shows the symtoms you describe. A lot of people wire the flap in the always open position instead of replacing it. All it does is restricts the exhaust flow to heat the cat up faster. If it remains closed it will restrict exhaust flow and the engine bog down. Sometimes it will also make an annoying metalic vibrating sound.
Calvin

[onthetrack01]

Thanks again for your response. I've just sent the car to the shop, along with your comments. I'll let you know (via response to this topic) what it turns out to be.

Thanks again! - Jason

[wcdeane]

I have a '91 SE with similar symptoms. The only difference being that it seems most pronounced in first gear. Let me know what you find out. I'd appreciate it. [e-mail]

[onthetrack01]

Update on the boost/RPM issue:

The shop has had the car for about a week. They are totally stumped. So the shop called Lotus USA this morning for some help, and the shop told me that Lotus gave them a big list of items to check. I'll post the resolution to this as soon as I know anything. Reading some other threads, the symptoms seem to be quite common.

Thanks again for everyone's help!

[wcdeane]

I know just how frustrating this must be for you because I just bought a ’91 SE, and the very same thing is happening to me. Here are some things that I have eliminated as suspect.

I have replaced the O2, MAP and MAT to no avail (would have replaced the TPS, but couldn’t find one locally). I have wired the EBP open to no avail. I’ve reset the ECM several times. Cleaning and gapping the plugs didn't help. Then I thought that I had a vacuum leak because the vacuum gauge was all over the place, but couldn’t find any leaks. So then I thought that maybe I had a burnt valve, so I ran a compression check, but found all 4 cylinders even at 140#. Then I really thought that I had something when I discovered that I had bad fuel and a clogged fuel filter. So I dismantled the entire fuel system, sent all 6 injectors in for a rehab, replaced the fuel filter, completely drained the fuel tanks – all to no avail. This is driving me nuts! I will keep you posted. You please do the same. Good luck!

[onthetrack01]

Update on the boost problem. Please forgive my non-technical explaination, I'll do the best I can.

It's not fixed yet, but we believe we found the problem. I guess there is a hose that runs from the dash to the engine compartment that has a leak. The tech rigged up a boost monitor to the engine, and the boost was fine, but it wasn't getting into the engine I guess. Not sure I'm getting this right, but he's trying to figure up the best way to replace or patch the hose without taking the dash out, etc. He figures this issue is confusing the ECM, and causing the symptoms described.

Any thoughts? This seems crazy.....

[wcdeane]

That's great! I hope that this solves your problem. But, is there any way you can be more specific about what hose we're talking about here? I am not aware of any hose that goes to the passenger compartment on any turbo model, unless it's for a mechanical boost guage, which I don't have. Could you ask your mechanic to explain it a little better, or maybe he could write it down for you. This is good stuff and it might be the solution to my problem as well. Please let me know.

[Arno]

I have *no* experience with Esprits, so please be gentle...

But on other turbo cars I have worked on which didn't want to rev above a certain rpm it often was the cat-converter (if installed of course) which had become either clogged up or had internally fractured and chunks were stuck in the exhaust pipe.

Both restricted the exhaust gas flow and caused the engines to get problems when trying to rev over 3000rpm.

The symptoms described here sound a lot like a partially blocked exhaust system to me..

Bye, Arno.

[cnh1990]

The only vac hose I am aware of in my SE is the heater acutuator vac line that goes into a T near the backbone on the left side of the car in USA Fed models. From the T one goes to the heater flap cam valve, then to the flap actuator to toggle air flow between the dash level vents and the footwells. The other side of the T goes to another cam valve that controls temp. Other lines that start to go up front are the MAP sensor line and turbo boost transducer line that goes through the same grommet to just above the right fuel tank area. Sometimes the acutator rod of the wastegate capsule can walk a bit coming off center of the capsule thereby making the wastegate inoperable. Also I have heard the hose going to the wastegate refered as a vac line. It according to the test descrption requires positive 9.5 lbs./sq. in. to test the wastegate movement. Lotus suggests using the hand pump for the seats to test the wastegate.

[wcdeane]

Arno: The cat is one thing that I had not considered because the car only has 25K mi., but considering with the bad fuel that I found in the car when I bought it, it is worth checking out. I may just take the thing off, regardless.

cnh1990: I thought that the AC/heater ductwork on turbo cars operated of a fan-belt-driven air pump? Am I wrong on this point?

As for the wastegate controls, all aspects of its operation seem to check out. There is free movement of the arm when air pressure is applied to the capsule, and the capsule does not seem to leak because it holds a vacuum very well. The only thing that I have not checked is the solenoid (for the lack of a better word) that modulates the air pressure that’s applied to the wastegate capsule. Does anyone know how to test this device???

One other thing stumps me. There is an airline that's attached to the Throttle Jack and the EBP solenoids (near the ALDL in the rear boot). The lines leading from these solenoids to the TJ and EBP capsules are sound and intact, and the TJ and EBP capsules check out OK as well. What I can’t figure out is where this line originates. It seems to come from nowhere. I think that it goes into the right sidewall of the engine bay, but I can’t say for sure. Does anyone know where that line leads? Does it go the intake manifold?

Keep the ideas flowing. I/we appreciate it guys.

[cnh1990]

Yes the Heater vac lines are driven from the pump in my Turbo SE. There appears to a T in the area of left gas tank and not quite sure where the other side goes to. I have seen people block off that line. My car did not seem to run strange when my heater was disconnected. I would think there is still a leak and would check the fuel pressure regulator vac line and the map sensor line. Also the line that runs to the boost gauge transducer. I have a feeling the MAP sensor is not reading right due to a leak somewhere. You don't think the manifold seals or throttle bodies are leaking do you?
Calvin 90 SE

[cnh1990]

Oh forgot, did anyone lean on or put pressure on the intake manifold, they have seals on them that don't like that sort of thing.
Calvin

[wcdeane]

There is no telling, but pressure to the intake manifold is a possibility. I never thought of it, but that is a really long lever. I could see where a little pressure out on the end of the air plenum could produce a lot of pressure at the base of the intake. I will check that out.

A guy should be able to re-torque the manifold bolts -- shouldn't he? By the way, the tops of some of those intake bolts/nuts are imposible to get at with a torque wrench. How's a guy supposed to torque them dudes to specs? Maybe I'm missing the right tools.

Walt

[cnh1990]

Walt,
Not sure of how to torque the bolts for the manifold. Will check when I get home.
But if the turbo only spools up to .5 bar it may be the wastegate solonoid as when it is broken or disconnected it will only allow about .5 boost or if it is stuck wide open it would give about 1 bar. I think that is what I heard. but if the 1 bar is held it would detect it as an over boost and fuel would be cut to the injectors.
Calvin 90 SE

[cnh1990]

Guys I just checked my flow chart for the vac lines. There seems to exisit a possibility that a vac line leak in the heater could affect performance, I am not sure how much though. For the Delco injection, a line from the vac pump goes to a T in the gas tank area, one goes to front compartment which was described earlier. The other side of the T when goes to another T and one side enters a Throttle jacking solenoid valve then on to the fuel pressure regulator on left side of the fuel rail. The otherside of T goes into exhaust back pressure valve solenoid that controls the EBPV flapper just after the cat. When I was replacing my heater cam valve I had my car at idle so I did not run my car to speed so personally it is unknown what a vac leak in this area would have on turbo boost. Any comments
Calvin 90 SE

[onthetrack01]

The clarify my earlier post, the tech believes that the hose which runs from the engine bay to the boost gauge in the dash has a leak (much closer to the dash than the engine), as he says that everything else is perfect. The boost lost from the leak is flipping out the ECU.

Can a hole in the boost gauge hose really expel that much boost?

(BTW: The manual boost gauge displayed 1 bar on testing. Turbo is fine. Cat is in perfect condition as well.)


>> Edited by onthetrack01 on Saturday 27th July 18:30

>> Edited by onthetrack01 on Saturday 27th July 18:31

[cnh1990]

It is not the actual loss in boost that will throw off the ECU. Could be that the MAP sensor may miss read and throw of the injectors. The fuel applied is supposed to be a constant difference between the AP and is confusing the ECU.
Calvin