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Old 01-27-2019, 09:21 PM   #1
LC4CARL
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Default Cuts out on accel

I submit to your superior wisdom, intellect and breeding, the following drive-ability concern:

The car:

'87 245 / M47 / B21FT swap. 740 turbo box, diverter valve routed back to intake, 3.0 bar regulator, breakerless distributor, LH2.2, orange tops.

The condition:

Generally runs great. 8 psi max. On occasion, in high-gear, at highway speeds, a light tip into the throttle yields a momentary engine "cut out." Like the fuel or ignition has been momentarily switched off, then on. It never feels like it's going to stall. But it is quite apparent to the occupants that there was a "hiccup." It's been happening for about six months now. This is a fairly repeatable condition. It does not occur under heavy throttle.

Thoughts, ideas?


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Old 01-27-2019, 09:34 PM   #2
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I'm no 2.2 expert, my first thought is throttle position sensor adjustment? I'm sure someone will have better ideas but I would check that
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Old 01-27-2019, 09:41 PM   #3
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I'd start with cleaning the MAF. In the winter my car would do that occasionally, regardless of throttle position. Sometimes it'd happen in the summer if the engine was still cold. Never figured it out.
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Old 01-27-2019, 09:45 PM   #4
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Start here: https://volvoforums.com/forum/volvo-...eration-45060/
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Old 01-28-2019, 08:01 PM   #5
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Much appreciated guys. I'll keep you posted. 90 days to Davis. GO!
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Old 01-29-2019, 12:18 AM   #6
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Played with the TPS. The 2.2 seems to be a basic idle and wide open affair. Swapped in my spare 007.

I wish I had a better sense of whether it is an ignition or fuel problem. With the old style “batch fire” EFI, it’s all or nothing.

Drive it tomorrow. Keep reading.
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Old 01-29-2019, 02:22 AM   #7
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591 vs 541?
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Old 01-29-2019, 03:19 PM   #8
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Ive had this same problem except with lh2.4. My wideband reads super rich when this happens.
Ive played with the tps as well to no avail. I've done/checked a laundry list of things, and it seems to be coming down to either o2 sensor or fuel computer.. Let me know when you figure your problem out!
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Old 01-29-2019, 07:41 PM   #9
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I had to set my TPS with a multimeter once to get rid of a similar problem. For some reason it just wanted absolutely perfect positioning. THis was odd but it worked. (LH2.4) Not saying that's the problem but it was doing a very similar thing.
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Old 01-29-2019, 09:04 PM   #10
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What shape are the intake hoses on the turbo in? They're known to get tired and collapse. I also had a similar issue with a cat that was plugged / going bad.

A long shot....if you're using the 700 airbox? was there any of that gawd awful foam still glued into the lid?
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Old 01-30-2019, 02:30 PM   #11
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Hoses are new. Cat is, well, installed. TPS and MAF worked OK with B230. Obviously the B21FT install changed everything. A fairly repeatable condition: high gear, light "roll on" of throttle equals "buck." Feels like a momentary suspension of either spark or fuel. Hope to have wide-band hooked up sooner than later. Perhaps a clue lies there.


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Old 01-30-2019, 04:15 PM   #12
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What does your boost gauge do when this happens? I mean is this happening as it transitions from a n/a engine to boost? If so there is enrichment that should be happening and also the spark needs to be very strong. Air leaks can be sneaky, too. so it can't hurt to double check. All of those things would affect the transition alot. The wide band would let you know more as you are going to find out.

Since you are in hgh gear it would seem to suggest a momentary spark blowout. High gear steady state and then making boost is a very tough situation with a high gear load about to become much more. Try a .026 plug gap. What type of plug are you using? Coil and powerstage connections clean and tight? Good heat sink goop on the powerstage? It may be that something like the coil or powerstage just aren't up to snuff anymore. I'd check the secondary resistance of the coil as well.

I like your swap the best! Only thing I'd do different is LH2.4 or megasquirt.
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Old 01-30-2019, 06:13 PM   #13
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I like your swap the best! Only thing I'd do different is LH2.4 or megasquirt.

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Old 01-30-2019, 06:23 PM   #14
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Hmmm, what about in tank pump stuff?

The in tank pump does tons of work, and the piece of hose between the pump and the sending unit could go bad and cause odd things to happen, especially when it warms up and under boost...

I had a weird stumble during throttle onset in a LH22 car, turned out the intank was clogged, and the piece of hose went bad like two days after I changed the pump

For the record I was able to tell something was up with the hose when the car ran terrible below about half a tank of gas where the hose would be exposed to air, and suck that up instead of fuel.
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Old 01-30-2019, 07:03 PM   #15
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Test drive!

Got in about 10 miles. Car runs great (well...). Cruising at highway speeds 60-70 mph. Light throttle. Only cut out once. It actually surprised me as I had given up intentionally trying to recreate the condition. On a mild grade, 65 mph, at little to no boost.

This is pretty typical. It may only happen every 10 miles or so.
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Old 01-30-2019, 07:07 PM   #16
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Hmmm, what about in tank pump stuff?

Worth a look. The two pumps are a year or two old. Just regular NA stuff though. New plastic line from chassis pump to motor. New / used 3.0 bar FPR.

Ever since I cut those springs...
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Old 03-09-2019, 08:06 PM   #17
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Made it to the coast and back. About a three hour drive. Only “glitched” once or twice. Grabbed an ignition box from the JY and put that in. We’ll see.


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Old 04-27-2019, 08:32 PM   #18
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Made SF for Davis. Car is a joy. Watching the new wide band during the rare cut out, the number holds steady. Just recently, during a more significant cut out, the tach and speedometer went to zero for a moment. I think that this last occurrence may be the best clue so far.
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Old 04-27-2019, 09:35 PM   #19
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Microsquirt with plug and play harness from yoshifab. Save up. I tune for u.
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Old 04-28-2019, 02:42 AM   #20
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Fuse 13? Is it clean with the contacts on the fuse block clean as well? If that fuse gets corroded, power to the instruments gets cut, and on certain 240s, it will also cut power to the fuel system.
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Old 04-28-2019, 12:27 PM   #21
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My 1991 740 Turbo is doing this too. It happened to me yesterday. I punch it and it just goes flat. I can hold the throttle and it will stay flat until I get off the throtte, then I can open the throttle again and the car will go. I haven't done any shakedowb, but it's how cars feel when they go full lean, they just won't rev.
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Old 04-28-2019, 02:23 PM   #22
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Just had a nice visit with an old Volvo tech at the show. He talked about 40 year old wiring. The odd thing is that it’s somewhat repeatable. I wonder if I hooked something up to #13 for power and that’s acting up.
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