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Roy Wicklund
12-29-1998, 09:13 AM
<i>I have a 1991 E30 M3 with stock engine, except for Autothority chip, that when first started the engine boggs down as if it isn't getting steady fuel or something, the it recovers, then repeats...sort of pulses. This is very noticeable if you put it in second gear and set the cruise control. After 3-5 minutes when the engine warms up the problem goes away.<p>I've had the plugs and O2 sensor changed, as well as a shop look at it and everything checks out OK, but no resolution to this problem. I'd appreciate any suggestions or thoughts. Thanks<br></i>

Steve
01-01-1999, 12:35 PM
<i>: I have a 1991 E30 M3 with stock engine, except for Autothority chip, that when first started the engine boggs down as if it isn't getting steady fuel or something, the it recovers, then repeats...sort of pulses. This is very noticeable if you put it in second gear and set the cruise control. After 3-5 minutes when the engine warms up the problem goes away.<p>: I've had the plugs and O2 sensor changed, as well as a shop look at it and everything checks out OK, but no resolution to this problem. I'd appreciate any suggestions or thoughts. Thanks<p>Did the shop check carefully for vacuum leaks? It's possible that the intake insulator gaskets are not sealing properly, creating a small vacuum leak. Lubro-Moly makes a leak detector spray can with special fluid that you spray around suspected areas and if your idle smoothes out and goes up suddenly, then you found your leak. WD-40 or something similar would also work in a pinch. What can happen is that as the engine warms up, the intake gaskets expand and seal vacuum leak so your symptoms disappear. I hope this helps. <br>

Scott
01-11-1999, 06:37 PM
<br>: : I have a 1991 E30 M3 with stock engine, except for Autothority chip, that when first started the engine boggs down as if it isn't getting steady fuel or something, the it recovers, then repeats...sort of pulses. This is very noticeable if you put it in second gear and set the cruise control. After 3-5 minutes when the engine warms up the problem goes away.<p>: : I've had the plugs and O2 sensor changed, as well as a shop look at it and everything checks out OK, but no resolution to this problem. I'd appreciate any suggestions or thoughts. Thanks<p>: Did the shop check carefully for vacuum leaks? It's possible that the intake insulator gaskets are not sealing properly, creating a small vacuum leak. Lubro-Moly makes a leak detector spray can with special fluid that you spray around suspected areas and if your idle smoothes out and goes up suddenly, then you found your leak. WD-40 or something similar would also work in a pinch. What can happen is that as the engine warms up, the intake gaskets expand and seal vacuum leak so your symptoms disappear. I hope this helps. <p>:I have a '89 M3 that suffered similar symptoms until such time as the intake manifold insulator/gasket was replaced - a $900 and all day job at a competent shop. If you get popping and other backfire sounds upon deacceleration, this may be a symptom of a vacuum leak from the insulator area. Another place to investigate would be the idle valve which, if on the way out, may cause an idle speed that changes from day to day. <p>


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