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'94 945T
I've been chasing this gremlin for over a year. When I think I have found it, it always reappears within a few days. Here is the symptom. It is most prominent after a deceleration but not always. Upon acceleration there will be a slight to very pronounced stumble. The tach drops and there is an associated loss of voltage at the coil. I am convinced it is electrical (there was a bad FPRly causing the in-tank pump not to operate but that has since been replaced with no change in the stumble). It seems to be more apparent in high ambient heat & when the engine is warm, on a cold morning it rarely acts up (but sometimes it will). It manifests with medium to heavy acceleration, a light foot usually has no stumble. At speed there is no stumble but, on occasion, hard acceleration when moving can result in a stumble.
I have cleaned all the electrical connectors (both cable connectors & component connectors) in the engine compartment with deoxidizer spray and have replaced the FPRly, RadioSuprRly, power stage, IACV, throttle switch, MAF & CPS. I've cleaned all the grounds I can find (engine & body/fender) About all I haven't poked around is the main computer.
Any ideas?
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1999 E320 1994 F150 (awaiting a new engine) 1989 560 SL 1994 945T (daughter's) 1986 242Ti (awaiting a B230FT transplant) 1968 GT500KR (under slow restoration) 2007 HD Nightster (son's ride)
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The only post that I have read about a hot stumble suggests a bad coil. Perhaps you can borrow or swap one?
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa
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"The only post that I have read about a hot stumble suggests a bad coil."
My '93 Regina had one caused by the RSR ground mentioned in earlier reply. Had it been a turbo, it would have affected the coil as well as injectors.
CLICK HERE.
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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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If you read BB, you would know that only about 15 new posts arrive daily on ALL the RWD categories. Even less on AWD.
There is no need to post 4 times, as the members who try to help out read the ALL tab.
I try to help out, but I also read to add data to my auto trivia search brain.
There are many more grounds than you might think,
- - -I've cleaned all the grounds I can find (engine & body/fender) - - -
These grounds are for components that do not ground by their body being attached to the engine or body of the car. For instance, the directional signal in a plastic body needs a ground wire,
For example, the power stage is attached to the fender - the attachment is its ground - I also read that there should be heat sink paste under it.
Have you checked this?
When I checked my '90 744 TI, I also found that there was a ground on the tower that held the anti-lock brake assembly - is it also grounded?
Any metal component that has only live wires to it gets its ground by its attachment.
One way to find a bad ground is ti run some extra temporary grounsd - if you do that one at a time, you may find the bad one.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa
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Thanks for the response but there is a mistakes in it.
The power stage does NOT ground through the attachment points, rather it grounds through pin #4. Very few components in a Volvo ground through attachment points. The only ign component that I know of that does is the spark plug. I am open to correction on this.
I am well aware there are quite a few ground points in the car and have cleaned the ones I have found. I am open to specifics on others I am sure I have missed but think I have gotten all of the ones associated with ignition components.
I did forget to mention I had replaced the ignition coil as well.
--
1999 E320 1994 F150 (awaiting a new engine) 1989 560 SL 1994 945T (daughter's) 1986 242Ti (awaiting a B230FT transplant) 1968 GT500KR (under slow restoration) 2007 HD Nightster (son's ride)
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did you solve your problem ?
I had (still sort of have) a similar ghost in my brick. Hot only symptom (after much "stop and go traffic"). I replaced and checked everything under the sun with some success. Spent about a year on the board bouncing ideas off everyone. My wire harness and grounds are in mint condition and I too replaced the coil. Only replacing the entire sending unit with the in-tank fuel pump improved my symptom greatly but not completely.
My latest idea - one or more of the "two prong" plastic connectors in the engine bay harness ( one to the TPS switch, one to the IAC valve, the four fuel injectors, and the Air Temp Sensor/regina ) may be getting heated up - metal expands, gets loose, missing voltage. Just a guess at this point, I got pretty tired of chasing this mystery and have learned to live with it at this point.
One thing I did find interesting, my RSR had failed and its only symptom was a "Hot - No Start" of the engine. It did not cause any stumble and would start up the engine when cold and run without any noticeable difference. After pulling the plastic cover off the bad relay, after close inspection, I could not find anything unusual or evidence of broken wires, melted or shorted connections. After replacing with new relay, the "hot - no start" condition was remedied.
If you have any news of your problem remedied - please share..
Thanks
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Dear Schumi1,
Hope you're well. When soldered joints fail, the cracks can be so small, that they are not visible except perhaps with very high magnification.
These micro-cracks result from the heating (expansion) and cooling (contraction) of the metals, as the current flows through the connectors. After enough cycles, the solder fatigues and cracks.
Re-flowing the solder - heating it until it liquefies (and the color changes from dull gray to a bright, shiny silver) = is the best way to restore proper function. It usually takes only a couple of seconds per joint, using a 15-20-watt soldering iron.
Hope this helps.
Yours faithfully,
Spook
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I thought that might be the case with the RSR..better to just bypass it or swap it out..pretty inexpensive part
thought I would share the info with others..
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