After Highway Driving

petershen1984 · Post by **petershen1984** » 03 Apr 2005, 10:19

Hey guys, I've been having a mysterious engine problem I can't figure out. It's just that, after a highway run where the engine's been running at 2,500 to 3,000 rpm, the engine feels really unresponsive (or sluggish) to my throttle input while accelerating from rest. This problem is persistent throught the rest of this engine's "operating session," and goes away when I next restart it. Sounds like a Microsoft problem?? Any pointers would greatly be appreciated.

Well, I know that dragging this heavy 740 is a lot of work for an old, underpowered B200E engine -- and I can only hypothesize that the mechanical throttle, when floored, introuduces more air into the intake than my engine is ready to combust at those speeds. Is there a remedy to this problem?

M Jarve · Post by **M Jarve** » 03 Apr 2005, 19:53

Did someone say turbo?

I've had a non-turbo 740 GLE and a turbo 940. Both used the 2.3L engine, and weigh about the same. But the difference in peformance is very stark. The 940 Trubo has the same acceleration and passing power as my Pontiac Bonneville SSEi (supercharged 3.8L V6); to be fair, the Bonneville has about 300-pounds on the 940.

ozzimark · Post by **ozzimark** » 04 Apr 2005, 08:45

i'll assume that it's not overheating?

petershen1984 · Post by **petershen1984** » 17 Apr 2005, 09:22

is what I described a sign of overheating? I *think* my thermostat was not reading any higher... this slow acceleration feels as if I'm giving too much gas and the engine's drowning in it..

Guest · Post by **Guest** » 17 Apr 2005, 17:28

have you checked the mass air flow sensor...

petershen1984 · Post by **petershen1984** » 27 Jul 2005, 08:05

Actually, I hypothesize that it's the idle air motor. My habit is to coast downhill and maintain speed limit (100 km/h), which means the throttle spends that duration of time in the closed position, while the IAC, along with the transmission's momentum keep the engine running.

Well, my problem is not limited to starting from the toll booth. My idle speed has been intentionally adjusted to 1,000 with electronics and air conditioning working; when the A/C clutch disconnects, my idle speed goes up to 1,500 (in neutral). I need it to be high to compensate for all the power used while the accessories are running.

Anyway - here's to the point: even with the above idle adjustment, after a highway run, my engine idles considerably stable at the quarter line between 0 and 1000 rpms, while in gear and A/C engaged. I'll see if I can scrap an IAC from my car's siblings.

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PS. When cruising on the highway and and walking on the streets today, I must have counted about five or six other 740s I encountered along the way - one was even painted WHITE like mines - It must have been a late US-version model with the 940 style front end, the original 740 trunk lid, but with the redesigned tail light shell (not the 3x2 cubes). Makes me feel proud of driving an everlasting Volvo!

My college-graduated friends (driving newer Japanese cars - a Mitsubishi Galant V6 (2.0) and a Honda Civic) saw my car today with the new rims. They looked inside and couldn't tell from appearance my car is more than seventeen years old!

adrianpike · Post by **adrianpike** » 27 Jul 2005, 11:10

How's your ignition system?

petershen1984 · Post by **petershen1984** » 27 Jul 2005, 21:57

One thing I didn't mention is how I could "reset" the whole situation by turning off and restarting.

I've replaced many ignition parts these past two years -- the stage amplifier, new distributor, cap, and wires, and outer fuel pump.

I thought the problem had to do with me kicking down at high speeds - yesterday I was accelerating to 75 mph / 120 km/'h on third gear, nearing 3,000 (OD gear) to 4,000 rpms (3rd). This is not a performance vehicle, but it gets to those speeds with time and patience

All belts are recently replaced, although the welded L-metal needs to be replaced (I'm hearing a more resonant chirp while cold again but that's burning off a new belt!)

petershen1984 · Post by **petershen1984** » 11 Aug 2005, 01:13

Okay folks, I had the problem resolved today - as it turns out, the vacuum hose can be the root of a lot of problems I've been describing lately. My car idle isn't controlled by a stepper motor (what then??), but after the hose was replced, my car can idle at 750 rom now and is barely affected by the air conditioning clutch. The highway problem might also be overcome!

PETO · Post by **PETO** » 16 Aug 2005, 20:57

NOT CHECK BUT CHANGE AIR AND FUEL FILTERS, PUT BOSH 4 SPARK PLUGS, 8 OR 9 MM WIRES AND NOT CHEAP GASOLINE AND YOU WILL TELL ME ABOUT IT !!!