'93 940 144k. After completely warmed up (usually on a hotter day here in the Phoenix area), the car is SOMETIMES very sluggish on acceleration until you get the rpm's up. Fine at highway speed, once rpm's are up, just no power at low rpm's. Frequency is once or twice out of every three or four accelerations from a traffic light. Never happens when car is cold. Doesn't always happen when warm, intermittently occurs when hot. Smacks of electrical to me, but haven't narrowed it down yet. (No check engine light or codes). Has a new fuel pressure regulator. Fuel pump relay is also new, and shows no cracks around solders.

Ideas where to start looking?

What have you done or checked? It may need a tune up, hoses, check the vac hose at the regulator? Dry air has to take it’s toll on these parts. The charcoal canister has to be removed to check the hoses (and the plug!) out thoroughly. Spark plugs, wires, distributor... Two of the five 940s I bought were found with the timing belt off the mark. One, only 1 tooth off on the cam and the other one was 1 tooth off on the crank. On the latter, the belt looked brand new, so fortunately it wasn’t like that long.

The ninety cent fix:
When I got my ’93 T-Rex (/Regina) driver beater* last December, it just was not performing well. Lousy gas mileage, 17 MPG, was bugging me. After driving it for a month I had a no start situation. For four weeks I checked everything, replaced everything. I was ready to pull the head after a compression test. Everything was at TDC when I pulled the valve cover and I saw that #1 cam lobes were not “perky” as it should be. The cam indexing pin was broken and the cam pulley had readjusted itself a little as time went on and eventually wouldn’t start. The new pin cost 90 cents. I went from 17MPG to, well, read my post above.

*Driver beater, meaning it’s for mileage accumulation plus it was very well dented buy the PO. I do take very good care of my cars though.
--
Tom F. Three 940s. The '93 T-Rex (Regina) is now running very well. Mods, RainX & cup holders. Lien holder on two more (the kid's). Rust In Pieces, '78 245

I don't have an answer but I've had similar problems with my '93 940 and Art Benstein has also reported this. In our cars the lack of power is very intermittant. It happened 2 or three times last summer and maybe twice this summer. My car has the Regina system so the FAQ are less helpful. I did the fuel pump relay resoldering, cleaned the throttle body and reset the throttle linkage to factory specs. I've replaced the crank sensor (for a no-start problem), the distributor cap and rotor, the plugs, and the spark wires. The car runs fine except for the occaisional power loss you describe.

Since it only happens in very hot weather, I'm thinking the problem may be fuel pressure related. I'd like to get a fuel pressure guage to check this. One outside possibility is vapor lock. The 940 runs pretty hot under the hood. If the fuel pump was weak, the check valve sticking, or the FPR bad this may be the result.

I'll follow any answers to this post with grest interest.

Jim, my car is the Rex-Regina system also. The fuel pump is 2 or 3 years old. Your idea is an interesting one - at least it gives me another place to look. A fuel pressure guage hooked up while you are driving would tell you instantly whether fuel starvation is the problem. The feel of the engine is as though the mixture is way too lean - doesn't buck or jerk or backfire, just doesn't go (much). Thanks for the idea.

Dear Abel,

May this find you well. When was the last time the trans fluid was flushed? Heat degrades the fluid's energy-transfer capacity. That is inevitable. However, the degradation will be faster in Arizona's searing heat, than in the relative cool of, say, Seattle. Towing also accelerates trans fluid degradation.

If more than 20K miles has passed since the last flush, I'd recommend:
(a) Getting 12 quarts of Wal-Mart fluid and flushing the trans (see the FAQs, under FEATURES, above, for the procedure).
(b) Drive for 1,000 miles with that fluid
(c) Re-flush using 12 Quarts of Mobil 1, Synthetic Fluid.

If the trans is the root of the sluggish acceleration, then you should see an improvement as soon as you complete the first flush. The synthetic fluid will hold up better, under the severe stress imposed by Arizona's climate.

On the other hand, if the fluid has been flushed recently, then the trans is not likely to be a cause of the sluggish acceleration.

Yours faithfully,

spook

Thanks, spook. I have considered the trannie, especially after my wife claimed that she saw the tach go up without the speed going up. I'm still skeptical on this possibility and want to check it out myself. Since the problem only occurs intermittently, it's hard to duplicate conditions and watch the tach. For example, when I asked my wife (it's her daily driver) how the car was yesterday, the reply was "no problems."

The trannie fluid was flushed about a year ago, BUT, it was in response to almost a chocolate milk appearing fluid that I attributed to a rubber trannie cooler hose breaking down. I ran 10-12 quarts through. Inspection of the fluid a few days ago revealed fairly normal looking stuff. One possibility still though - maybe some gunk gets sucked into the trannie filter and impedes flow. Still seems like it should occur regularly, though, and not intermittently. I plan to move to synthetic fluid soon, and when I do I'll change the filter at the same time.

You should start with the 700/900 FAQ here on the site:

http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm

Particularly:
http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#NoorSlowHotStartroblemDiagnosisandRepair

Chris
--
1991 Volvo 945Ti @ 0.322 million kms, in Ottawa, ON, CANADA

Spent alot of time there already, thanks. It's an excellent resource. In my case, the car starts fine, never dies, idles fine, just loses power intermittently when hot (but doesn't buck - still runs smooth). Sometimes when you post a problem like this one, another volvo-ite has just fixed his/hers, and gets you right to the point.