Under a very specific set of circumstances I have a rough run/hesitation. I wouldn't say that it is a starting issue in the traditional sense as the car starts promptly on first crank cold, warm or hot. Runs well and idles smoothly, seems to be on point for power all with the exception of the following. The problem is only directly after warm start. Car starts easily, idles well for about 30-60 seconds and then revs drop and hunt (300-700 ish) for 30 seconds - 2 minutes. It almost feels like the car will stall but hasn't (yet...). While this is happening if I depress the gas pedal there is no power (extreme hesitation). If I am attempting to drive the vehicle at the time (got caught out before I recognized the pattern) it's a put-on-the-hazards-and-roll-to-the-curb situation. If the rough idle occurs for longer than 30 seconds it will throw a code. Stomp test shows 1222 lambda – fuel too lean/rich, there is a strong smell of raw fuel, so educated guess, too rich. After the 30 seconds - 2 minutes the revs even out and everything is back to normal. This only occurs after warm restart when the car has been running for more than 10 minutes and then sat for more than 5 minutes. If I turn the engine off and immediately restart it does not happen. If the car sits for more than 2 hours it does not happen. It occurs consistently, which is at least helpful for diagnosis purposes, but is getting worse in that the duration of the rough idle is increasing.
Car is a 1989 BMW 325i. Manual trans coupe, build date November 1988. I know little of the history of the car. One owner for the past 20 years, it sat for about a year before I bought it. PO broke timing belt and had top end rebuild a couple years before parking it. I have had it back on the road about 1 month, currently a resto project/occasional driver for me.
Work completed:
general maintenance: oil change, new fuel filter, new air filter, replace front brake hoses, replace spark plugs, replace diff and trans oil, replaced battery, new trans mounts
in search of cause of rough run: replace cracked oil filler cap, replace cracked air intake boot, replace vacuum line to evap canister, check for vacuum leaks with carb clean (none found), test coolant temp sensor (in spec as per Bentley manual), check wiring coolant temp sensor to dme (good), check and clean C191 multiplug (no corrosion noted), run seafoam injector cleaner through tank and running 94 fuel (two tanks of fuel ran through so far).
I am stymied as to the cause but this may be due to a lack of understanding on my part about what system (other than temp sensor) has input on warm start. I am new to working with e30's, but this seems too consistent for a failing fuel pump, not often enough for a vacuum leak, I wondered if a leaky injector is flooding the cylinder but suspect that would require a longer/multiple crank to start (?). I welcome any thoughts or guesses on what to check next. Here's to hoping there is an obvious suspect to the e30 enlightened!
Car is a 1989 BMW 325i. Manual trans coupe, build date November 1988. I know little of the history of the car. One owner for the past 20 years, it sat for about a year before I bought it. PO broke timing belt and had top end rebuild a couple years before parking it. I have had it back on the road about 1 month, currently a resto project/occasional driver for me.
Work completed:
general maintenance: oil change, new fuel filter, new air filter, replace front brake hoses, replace spark plugs, replace diff and trans oil, replaced battery, new trans mounts
in search of cause of rough run: replace cracked oil filler cap, replace cracked air intake boot, replace vacuum line to evap canister, check for vacuum leaks with carb clean (none found), test coolant temp sensor (in spec as per Bentley manual), check wiring coolant temp sensor to dme (good), check and clean C191 multiplug (no corrosion noted), run seafoam injector cleaner through tank and running 94 fuel (two tanks of fuel ran through so far).
I am stymied as to the cause but this may be due to a lack of understanding on my part about what system (other than temp sensor) has input on warm start. I am new to working with e30's, but this seems too consistent for a failing fuel pump, not often enough for a vacuum leak, I wondered if a leaky injector is flooding the cylinder but suspect that would require a longer/multiple crank to start (?). I welcome any thoughts or guesses on what to check next. Here's to hoping there is an obvious suspect to the e30 enlightened!
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