oldstyle Posted September 14, 2013 Share Posted September 14, 2013 (edited) I got in my 93 Riviera today and noticed a stumble at idle. I tested the car at freeway speeds and can still feel the car stumble but not as often. The IAC and plugs/wires are fairly new. The car starts up with no problem and hasn't actually died. Just feels like it will. Unplugged the MAF and that seemed to make no difference.The Delco coils each read 6.1k ohms (tested with wires removed but harness plug installed).I plan on changing the TPS tomorrow. If that doesn't work Ill check fuel pressure.Any other thoughts? Edited September 14, 2013 by oldbuickone spelling (see edit history) Link to comment Share on other sites More sharing options...
padgett Posted September 14, 2013 Share Posted September 14, 2013 (edited) Does the Riv have the diagnostics capability the Reatta does ? If so you can shut down injectors manually to see if one makes no difference. Otherwise you need to do it manually by disconnecting injectors. (Less strain than plug wires). Edited September 14, 2013 by padgett (see edit history) Link to comment Share on other sites More sharing options...
oldstyle Posted September 14, 2013 Author Share Posted September 14, 2013 I believe so. Ill check my service manual to see if I can turn the injectors off. Link to comment Share on other sites More sharing options...
oldstyle Posted September 14, 2013 Author Share Posted September 14, 2013 (edited) Changed the TPS and still have the same issue. Turned off each injector from diagnostics. Injector one off seemed to smooth out idle ( did this a few hours later and didn't notice the idle smoothing out) but ran much rougher when applying some gas. All other injectors caused a difference at idle and with gas applied.Parameter Idle ED01 THROTTLE POSITION .4 ED04 COOLANT TEMP 83ED06 INJECTOR PULSE WIDTH 4.4-5.0 ED07 OXYGEN SENSOR .10-.89 ED08 SPARK ADVANCE 17-21 ED11 ENG RPM 620-750ED16 SPK ANGLE kNOCK RET 0 ED17 OLD PAL KNOCK SIG 122 ED18 OXYGEN CROSS COUNTS 0 ED19 FUEL INTEGRATOR 123-131ED20 BLM FUEL 129 ED21 AIR FLOW 5 ED22 IDLE AIR CONTROL 29ED23 MANIFOLD AIR TEMP 27 ED24 COMMAND RPM FOR IDLE SPEED 675 ED25 CCP DUTY CYCLE 17 ED26 AIR FLOW RATIO 14.4 ED27 WEEK CYLINDER 0 ED98 IGNITION CYCLES 1 ED99 PROM 2894 Edited September 14, 2013 by oldbuickone (see edit history) Link to comment Share on other sites More sharing options...
oldstyle Posted September 15, 2013 Author Share Posted September 15, 2013 Fuel pressure at idle is 35 lbs.Put a spark tester in between coil and spark plug wire. Looked good. Ill start looking for a vacuum leak in the morning. Link to comment Share on other sites More sharing options...
padgett Posted September 15, 2013 Share Posted September 15, 2013 Looks reasonable. Might try switching the #1 plug/wire with #3 if it will reach. Sounds like marginal (hardest to find) secondary ignitions or a slightly dirty #1 injector (or, or, or,,,) Link to comment Share on other sites More sharing options...
oldstyle Posted September 15, 2013 Author Share Posted September 15, 2013 I know, seems like it could be anything. Replaced some questionable vacuum lines. No change. I did notice that it runs good when cold. When warmed up it starts acting up. When warm it stumbles every 30 seconds or so. Ill pull the plugs after it cools a bit. Link to comment Share on other sites More sharing options...
oldstyle Posted September 15, 2013 Author Share Posted September 15, 2013 Ordered ICM and coils... Link to comment Share on other sites More sharing options...
oldstyle Posted September 29, 2013 Author Share Posted September 29, 2013 Thought I'd update this because the problem is solved. Maybe it'll help someone else.Changed the ICM and all three coils. Problem is gone...finally. Link to comment Share on other sites More sharing options...
D-a-n-i-e-l Posted September 29, 2013 Share Posted September 29, 2013 So you had one bad coil? Link to comment Share on other sites More sharing options...
oldstyle Posted September 29, 2013 Author Share Posted September 29, 2013 Im assuming so. But I changed the ICM and all three coils at the same time. They all read good but one must have broke down under voltage. Or it could have been the ICM, not sure what symptoms that alone would give. Link to comment Share on other sites More sharing options...
oldstyle Posted October 31, 2013 Author Share Posted October 31, 2013 UpdateCar started stumbling again. Also, error 42 c in computer. Ended up being the coil for plugs 1 and 4. Next day same coil again. Not sure if it's poor quality of the coils or something else (spark plug wire). Link to comment Share on other sites More sharing options...
padgett Posted November 2, 2013 Share Posted November 2, 2013 Nice thing about a Delco is that you can swap coils and see if the trouble follows the coil or is related to the position. Link to comment Share on other sites More sharing options...
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