240 Extreme hesitation when accelerating

It's a 1982 244, which I've swapped in the running gear from a 1988 740 turbo.

It's been running fine until today, if I accelerate slowly, it's a bit noticeable, and if I floor it, it'sjerky and hesitates a lot. It's like a fuel supply issue, but I'm sure it's not. It seems to idle fine, and it's builds low boost.

Checked for air leaks, checked the FPR, checked all connections, everything seems OK.

Any suggestions?

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Comments

  • Try a new set of sparkplugs

  • The spark plugs are less than 12 months old, as are the leads

    I did however try a different coil to distributor lead this morning, and it made a difference, although still running bad

    When I finish work, I'm going to grab a new ignition lead, and swap out the coil, as I have a known good one here.

  • Felt like that for me - stuttering under load - as my fuel pump was failing. Check that both your pumps are working/the electrical connections are tight on the under car pump and your fuel pressure is adequate

  • carnut222Greg S @carnut222 Daylesford VIC

    And your air inlet hoses are OK (I’ve heard of hoses collapsing between the air filter and turbo if they are soft. Unlikely but something to check.

  • edited March 29

    I replaced the coil and lead yesterday with no improvement. When I came home from my test drive, there's some smoke coming from the turbo manifold, around spark plug 3.

    Once it cooled, I investigated a bit, seems a bit oily in that area, and I'm low on coolant. Will have to investigate this before anything else, likely to be related to my issue. Does a blown head generally have an external leak?

  • edited April 3

    Coolant leak ended up being a loose heater hose.

    So I took off the intercooler piping, and there was a lot of oil on the intake side, MAF was soaked.

    I cleaned it all up, went for a drive, no improvement.

    It's revs and redlines fine in neutral, but even in first gear, hesitates by 2k RPM, and won't really rev higher than 5k


    Im stumped

  • carnut222Greg S @carnut222 Daylesford VIC
    edited April 3

    Is your MAF upstream of the turbo (where it’s meant to be) or downstream of the turbo? How could oil get in the MAF if it’s like factory setup which IIRC was this flow: air filter -> MAF -> crankcase oil breather hose -> turbocharger -> intercooler -> inlet manifold. Seems like the only way that could happen is if you’re getting reverse flow from the intake back out through the MAF...for example if you have no compressor bypass valve, bad rings, and when you let off the accelerator it pressurises the crankcase due to the compressor surging and that forces oily air back out thru the intake...wacky theory anyway!

    Oil on the intake pipe going from turbo to intercooler could be coming from the turbo or the breather...IIRC the breather goes into the system before the turbo.

  • edited April 3

    That's the correct setup, and it's what I'm using. I'm just using a pod filter, and from the turbo, it's angled downwards, so any small amounts of oil making it that way is just following gravity.


    CBV is still in place, as factory, and pretty sure it's operating. PCV system was serviced not long ago. Maybe I'll check the PCV and report back.

  • carnut222Greg S @carnut222 Daylesford VIC

    Odd, still don’t see how the MAF could be oily...unless it’s oil from the pod filter (is it like a K&N where you put oil on it? Could it have been excessively oiled, and that fouled the MAF?)

  • Yeah try another AMM, it would be something small

  • buddyglitchTommy @buddyglitch Melbourne
    edited April 4

    Turbo seals might be on the way out, leaking oil back through the intake. I had that happen when mine blew. Might be worth angling your intake hose + AMM so that they're above the level of your turbo and PCV recirc hose - instead of angled downwards like you said.

  • I haven't had much time to look at the car, hoping to have a couple of hours this arvo.


    After cleaning the MAF and all the oil (it wasn't a small amount, at least half a cup), it still ran like shit. I tried to floor it, and it really just gets worse as the RPM's get higher. I do have a good MAF here, but I'm hesitant to try it as I don't want to cover it in oil, but I will try it just to be sure.

    I don't have a lot of wiggle room, but I did angle my intake piping up slightly to hopefully keep the oil away from the MAF.

  • carnut222Greg S @carnut222 Daylesford VIC

    Can you upload a few pics - maybe showing how the MAF and air filter are mounted in the car?

    BarelyRunning
  • Sure thing, when I knock off work. It was completely fine for a long time, which is why I'm so confused.

    carnut222
  • Haven't had a chance to play, but this should give you some idea. No air leaks at the joiners or anything.

  • carnut222Greg S @carnut222 Daylesford VIC

    Thanks for pics. Why is the vacuum hose not connected to the compressor bypass valve? Do you have a different one elsewhere?

  • It was split when I got my 740, and has run without one through 3 cars, never really had an issue. What's the importance?

  • Ouch.. You'll definitely want to run that vac line.. The importance is it needs to see positive and vacuum pressure to close and open respectively. As it stands, it might sound cool, but you're leaking boost, running richer and making less power. If you want to delete the cbv properly, remove it, blank it off with a blanking plate and block the hose at the throttle body.

    BarelyRunning
  • Hard to tell from the pics but have you checked the directional arrow on the MAF? It needs to have the arrow facing the turbo inlet.

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