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Engine Specific Info and Questions => IDI Engine => Topic started by: Gizmoman on December 19, 2017, 09:11:53 am
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Hey all,
I have a Holset on my 1.9 and can seldom get over 10-12 psi - I even have the wastegate wired shut :o. I have seen 18 but not for some time now. It seems fairly obvious to me that I must have some boost leaks. I did a leak test many months ago, found one and fixed it. I still cant get my boost where I want it to reach which is 20 psi.
During the leak-down test, I could hear air going into the motor and figured it was because I didn't have the engine at TDC. Why I didn't just crank it a bit to close the valves I don't recall but I must have figured the leak I found was the culprit - apparently I have more leaks or there is some other issue.
To explain how it feels when driving, when I get on a freeway on ramp and floor it, boost climbs quickly to about 10-12, then the engine begins to stumble like it's running out of fuel and boost stops climbing. I back the pedal off a tad and it smooths back out - add pedal, stumble - like I hit a wall.
I have messed with the LDA, changed springs, and adjusted the LDA spring seat plate and while it did seem to help some, the problem still exists. I can get a bit of smoke if I really tromp on it and I'd rather not turn the fuel screw any more as my mileage is already not that great.
Other than this one issue, the engine runs like a champ - thanks to a lot of help I have received here. I'm going to do another leak-down test this morning and would like to know if having the valves closed (TDC) is required. Also, if anyone has any other reasons that could cause this stumble/low boost issue, please let me know.
Thanks,
Jim
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I haven't done this but have considered it. I think it would work to loosen the cam caps in order to make sure all 4 intake valves. Plug the air filter inlet. Apply your boost pressure to the crank vent intake port. Any valve leakage will be heard going into the case. Otherwise, it should hold pressure.
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Well. changing the seeping boost connector did nothing. Boost still quits at 10 psi and I have to back off on the throttle or it feels like it's running out of fuel.
It's still pretty peppy so I'm going to drive it from San Diego to Eureka tomorrow but it sure would be nice to have more boost - especially going up the grapevine (about 12 miles of 6%).
I think my LDA is still wonky - it just seems to stop fueling at 10 PSI but I don't have time to mess with it before the trip.
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IIRC there will always be one intake valve open at least a little. I would take it apart at your connection to the intake manifold and test from there.
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IIRC there will always be one intake valve open at least a little. I would take it apart at your connection to the intake manifold and test from there.
Thanks theman53 - good to hear from you. If you recall, I built the intake myself and may have a cracked weld or a bad seal at the head. However, spraying soapy water while under pressure doesn't reveal anything. Still worth a complete going over though.
I'm starting a new thread as I believe my low boost issues are related to low fueling. It's a long, wordy post but of you have any ideas, please let m know.