Hey guys, recently i inherited my dad's car (died on Nov 1st) it's a 1989 daytona 5spd, 2.5 l4 w/ turbo. now a few weeks ago when he was driving it we noticed that all of a sudden it seems to "overboost" now i havent had a chance to look at it for a few days since it's parked about 30 km from me. any ideas as to what might be the problem?

Overboost? How do you know it is overboosting, and what does it do?

well what happens is if you give it too much throttle aka: "flooring it" it will cut the fuel for a split second (im guessing to avoid engine damage)......a friend of mine thinks it might be a vacuum leak???

I think your more confused then we are, first: is it really overboosting ie boost creep as in boosting more psi then then the wastegate is supposed to let it, OR are you just overrevving it and the rev limiter is cutting off the fuel?

it will cut the fuel way before it gets to redline (still at full boost) and when it cuts the fuel the boost will drop a few psi and go back to full and start doing it again.....remember....it just started doing this about a month or so ago. as long as you dont quite give it full throttle it will act normally.

I think I ate too much tortellini.

Sounds like a fuel delivery issue to me.

Check your filters...

Sorry to hear about your old man, what a blow.

I don't trust my knowledge on turbos to be sufficient enough to give you reliable help, so I won't try...
SponsoredLink and Red_Eyed_Honda will know ths resource: http://www.boostvalve.com/1.8info.html

Is it automatic? It sounds like it's just downshifting slowly, and this would make you think its "overboosting", because of the increased revs and power.

Is it automatic? It sounds like it's just downshifting slowly, and this would make you think its "overboosting", because of the increased revs and power.

he said it's a five speed.


To me, it sounds like it just can't handle being romped on. maybe it's missing or something.

change all the fuel filters, give it a complete tune up, and check all the vacuum lines

I know that the fuel filter and pump where changed about 6 months ago when it had alot of work done (like $3,000 worth of stuff)......but the next time i get out to it im gonna check the ignition wires and plugs and see if i can find any bad vacuum lines. Thanks for your input guys!!!

might be some sort of fail safe mode for the ecu, if its running too lean it might cut back boost, but it being an '89 i'm not 100% on it. were bigger injectors and higher flow pump added if boost was upped? how's the boost controlled? if a manual boost control was added, maybe turn it back a little bit and see if that helps.
when were the spark plugs changed? that would cause issues at boost if they're old.
go for ngk copper plugs if you do change them, they're cheap.

but is it running more boost than stock? thats my important question.

(i would hold on to an '89 daytona turbo, its going to be a classic, only if it was a shelby)

this car is completely stock, and no.....it's not a Shelby (because when my dad bought it he wanted the 2.5 over the smaller 2.2 that was in the Shelby models, thats really the only reason he didn't get a Shelby. But yea....i completely forgot about the spark plugs, think they look like the originals ): i probably should buy new ones but dont i need a gap adjuster tool as well? also....i put 1/2 a tank of 94 octane in before i parked it so im pretty sure it's not running lean. but yea......im definitely going to hold on to it (unless i have no choise but to sell it down the road)

Running lean doesn't have anything to do with how much or what type of fuel is in it. The first thing I would do is head to your local Autozone or somewhere else that has a loaner tool program, get a fuel pressure gauge. Find the Schrader valve (looks like a tire valve) on the fuel rail, hook it up and temporarily mount it so you can see it with the hood closed. Drive around with a passenger who can read the pressure, and replicate the problem.

this car is completely stock, and no.....it's not a Shelby (because when my dad bought it he wanted the 2.5 over the smaller 2.2 that was in the Shelby models, thats really the only reason he didn't get a Shelby. But yea....i completely forgot about the spark plugs, think they look like the originals ): i probably should buy new ones but dont i need a gap adjuster tool as well? also....i put 1/2 a tank of 94 octane in before i parked it so im pretty sure it's not running lean. but yea......im definitely going to hold on to it (unless i have no choise but to sell it down the road)

i would find out what the gap and heat range is, an autozone or comparable store or the internet can tell you. with the ngk's you can get them pregapped, but those gapper tools are cheap enough to make sure they're gapped properly.