The other day I notcied the idle on my 1989 745GL (B230F, LH 2.4) surges after about 5-10 seconds. This only happens when the car is warm and I can only detect it in P or N, but that doesn't mean anything I think. So far I have done the following to try to elminate possible problems:
1) Check the ECU for fault codes -- none
2) Run through the LH self diagnostic mode -- all seems OK.
3) Inspect various vaccum hoses to see if they are cracked, loose etc.
4) When pulling the main hose to the IAC motor and plugging it the engine
speed goes down to a base idle level that I think is plain too high ~700.
I have not yet checked the MAF voltage. I don't know what voltage it should output at idle, though given that when I yank the MAF connector the car clearly goes into limp-home mode I'm not directly suspecting the MAF.
My understanding is that this car does not (unlike some other FI systems out there) have a secondary idle bypass valve.
I have not checked O2 voltage yet. I guess it could be stuck low and thus telling the ECU to dump more fuel in. Hmm, in fact, as I'm writing this I relaize that if the O2 is the problem that could account for the fact that the problem doesn't show up until the car is warm.
Any good thoughts anyone?
In reference to Claes' idling problem, Glen writes:
If the Throttle Switch was set wrong or not giving a good "Throttle Closed" signal it would soon set a code. Plus as Claes states he ran it through the LH self diagnostic mode. One step of this test checks the output signals given from the Throttle Switch a missing signal would have show up then.
I agree with the theory, but inaccuracies in the throttle plate clearance may be exacerbated by poor microswitch adjustments. I have found that a poorly adjusted micro-switch does not always trigger a fualt code.
And last, NO 700 rpm is not too high for a base idle speed. In fact it's perfect, you set it any lower and you'll get the ol' start and die syndrome, especially now with the cold weather coming on. If you lower it to 650 I guarantee you it will start and die first thing in the morning. I wish I had a dollar for every base idle I set up to 700 to get rid of Ol' start-n-die.
You will note that I said that the engine should stumble or die with the IAC hose pinched off and that a response idle of 700rpm (not base idle) is too high. That being said, Volvo TP 32394/1 section WA2 states that the throttle body should be set up to allow a base idle of 480-520 rpm. My car has been set to the spec. At -40F (way up here in snowy Canada) my Brick fires up cleanly at 520 rpm, does not stumble or hesitate and has never stalled on start up. I go with the spec.
Now, with automatic transmissions, setting base idle is even more important. One does not want to go too high on idle because in "Drive" this puts load on the torque converter when stopped for a light. This may not amount to much, but I am a minimalist when it comes to loading up mechanical parts!!
I say there's nothing wrong except maybe a dirty throttle plate. Take the intake hose off the throttle body and take a look, if it's dirty spray some cleaner on a rag and wipe it clean so you don't kill the O2 sensor with the spray cleaner.
Good point. I agree. Sometimes its even easier to do a complete job just by removing the thing altogether.
SAE J-1930 implementation they are known as ECM's (Engine Control Module) and not ECU's (Engine Control Unit).
Good point, Glen. Sometimes I have to refer to that Volvo tech tip which says that the AMM is now a MAF, and vacuum is now MAP. And I thought I had troubles switching to metric...... :-)
Thanks for the comeback Glen. It's so nice to talk about these kind of issues and not have to get into the Type "C" or "Sierra" discussions. Makes my noggin work a little harder!
The Gothenburg Bible
34 Ullswater Dr
Nepean, Ontario, CAN
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Some time ago I posted a question regarding replacement of the distributor seals on a B230F. My engine had developed a small oil leak around the distr. A few people wrote me that they were also interested in finding out how to perform this repair, so for those and anyone else interested, here goes:
First, my thanks go out to Glenn Thompson for giving me some very useful pointers and telling me that it really isn't a very difficult procedure. And indeed, I can now confirm that even for an amatuer like myself, it isn't. I performed the surgery last night. It took me about an hour. AND, now my engine doesn't leak oil from the distributor any longer!
Some good pointers (some of which are Glenn's):
Make sure to mark the position of the distrbutor. That way there's no need to check the timing afterwards.
There is enough space behind the cylinder head once the cap and rotor are off. I found that the use of a dentist's mirror offers the amateaur an excellent view of where the THREE screws that hold the cap in place are located. A short 8mm box end wrench worked great to undo them.
A 10 mm wrench is all that was needed for the TWO bolts that hold the distributor to the cylinder head.
When reassemblying, coat the smaller of the two o-rings with a little grease. For the non-purist, a small amount of silicone on the bigger o-ring will ensure even less chance of a leak in the future.
The two o-rings ran me just over $1 at the dealer.
This was on a B230F. On these engines the distributor has no other electrical connections than the 5 H/T leads to the cap. On B230FT engines the distributor also has a hall effect switch in it (a cam postion sensor), so that adds a couple of wires, but shouldn't really affect the procedure in any dramatic way.
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