Tip-in hesitation

[alphajesse]

Hello everyone.
First: sorry to ask a question that probably gets asked often, but the search feature didn't reveal any definitive answers to my question or solutions to the problem.

A friend of mine just got a 1984 Regal T-type. The car is great! You guys are lucky to have them. It has a cold-air type intake with a K&N cone filter, an upgraded turbo of some type, dual 3" exhaust and now it has some skinnies up front and some fat slicks in the back. It is also equipped with a posi rear end, and a TH350 transmission. The body has 140k on it, the engine and trans, 5k. Got a great deal on it.

The car has pretty severe hesitation/stumbling on quick throttle opening- even just to 50-75%. I'm familiar with turbo lag, that's not what we are experiencing. It also doesn't feel like the transmission is slipping. The engine almost feels like it is attempting to stall.

What exactly causes this?
A full tune up is in the immediate works (plugs, wires, clean filter, oil & filter change) but I get the feeling that this won't fix it. The car is fine once it's going, so I don't think it's the coil packs. My personal turbo car (a Mitsu) would fall flat on it's face at higer RPM under boost when the coil was dying.
The threads I found all mentioned that the MAF, the ECM and the coilpacks could be the problem. In my case, which would it most likely be?
How can I narrow the problem to a specific system?

Also, what fixes this?

If it's the coils, new ones of course, but if the MAF or ECM, are they repairable, or must they be replaced? Where is a good source of parts if replacement is required?

Thanks for the help!

 

[turbo6x2]

Plugs are really important in these cars, wait until after the tune up then see if you can locate a MAF to swap and see how the car responds. It could be any one of the items you mentioned...

 

[Black Cherry T]

I had this same problem, after going to a bigger turbo and bigger injectors.

Since you have said the car has an upgraded turbo, it may also have larger injectors too. If it does, then it must, of course, have a new chip programmed for the injectors. You should check this out.

After you have done a tune up, and you still have the problem, like I did, perhaps you may find what I found with our car interesting. But first, a couple of questions...a) do you know what size the fuel injectors are?...b) what fuel pressure do you have at idle, with the vacuum line off?

In our '84, I was used to running about 40lbs of fuel pressure (vac. line off). I installed a new TA-49 and 009 (42.5lb) injectors, as well as a chip programmed for the 009's. The car wanted to stall and almost die with 50 to 75% pedal quickly applied from a dead stop. With a scan tool (OTC monitor), I noted that the MAF sensor reading at idle was 7 to 8. This in fact was too high - it should have been about 4 to 5. This higher reading that the ECM saw, caused the ECM to put more fuel to the injectors, causing a rich condition at idle, and the BLM number to be 105. Changing the MAF sensor improved things - the reading at idle was now 5. And, the BLM jumped up to 115 at idle - better, but not perfect. I road tested the car - still seemed to be doing the same hesitation from a dead stop. Cranked the fuel pressure down 3lbs. Car seemed to improve a little. Cranked fuel press. down into the low thirties. Now, the car really came alive from a dead stop - no hesitation, no stall, and BLM numbers at idle were much better - at 128 to 132. But, what remains to be seen now, since I haven't put it on a 1/4 mile track yet, is what happens on the top end....if that low of a fuel press. will cause the car to lean out. It depends on how my chip is programmed. A scan tool is really necessary to tune these cars (watching the O2 readings, etc). In my case, it was hard to build boost, and leave from a dead stop quickly, probably because the turbo needs HOT exhaust gases to spool up quickly, and you can't get that if you are overly rich in fuel at idle and at lower rpms.

Hope this helps somewhat.

Wayne

 

[alphajesse]

That looks good. I'll check out the specifics with my buddy.

 

[WFO]

yeah,do your tuneup first and see how it feels.put in some ac cr43ts's gapped at a tight .035".

you're on the right track with the coilpack/module,they'll usually take a dump when they get some cylinder pressure(under boost).

my opinion is that the best thing anyone can do with these cars is to get a good scan tool(turbo-link),upgrade the ecm and buy a 16 position maxeffort chip.they are tuneable from top to bottom,just like a dfi.once you get the hang of it you won't know how you lived without it.

need that leaner idle? "click-click-click" *done*
need more fuel at wot? "click-click-click" *done*
want faster spoolup? "click-click-click" *done*

it's just that easy.you'll hear a lot of "experts" on this board whining about the poor spoolup and crappy idle on a hotair.you will find that these people are usually running some 15 year old chip that their cousin's buddy down the street burned on his atari 2600

my car idles like a sewing machine(with both side poly mounts)and spools way better than it ever did stock.oh,and i'm running the spearco front mount that "causes tons of lag and a crappy idle"(according the the experts).

later,sean

 

[alphajesse]

One more quick question.
All the 'hot-air' cars have the compressor housing after the TB, right?
Some guy my friend met told him to get a BOV to help with the hesitation. With the placement of the turbo on this car you can't use a BOV, and there isn't a need for one...
The guy my friend talked to, though, had an '85 and claimed to be running a BOV. I thought 83-85 cars were configured the same way.
Wouldn't he need to have converted to an IC setup to make it useful?

 

[WFO]

"the guy" needs to put down the crack pipe.

you are correct,the tb is before the turbo and even if it wasn't a bov wouldn't do anything about a tip-in hesitation.

 

[racemybuick]

No need for BOV

If you have a hot air car, there is no use, or even placement for a BOV. If your car has larger injectors, you may need to play with that little old FP Regulator. Do you have a guage on the rail? Is the Regulator an upgrade? If not, change it out for a Poston, or other GN vendor piece, and get a guage on the rail, then set your adjustments. Make sure you know what injectors you have, and what chip you have before messing with any settings. YOu have to know the car inside ot before you begin to work it up. I had my car apart twice to find mistakes and other faults the guy before me did to my car, and I still have issues that I am tying to relieve. Good luck!

John

 

[WFO]

Originally posted by alphajesse
a TH350 transmission.

just to clarify:you're sure it has a th350 and not a 2004r?

any idea what torque convertor is in it?these cars came with a 2400 stall stock and they need some convertor to get exhaust velocity/volume going.

if the tranny shop stuck you with some 1500 rpm stall it's gonna be a bit sluggish down low .

 

[alphajesse]

The guy the car was bought from claimed TH350.
The friend who bought the car has been under it enough to have seen if that was correct. Luckily my friend knows his old-school GM autos (he builds race cars, but fuel injection/ECU/ and turbos are out of his areas of expertise) don't know the stall speed, but can find out, I do know it's got a manual valve body.
Haven't been down for a couple of weeks to investigate the FPR, and injectors. Any way to identify chipped ECUs on these cars?

 

[Mr.Buick]

Max Effort Chip

Tell us more about the Max Effort Chip, where do you get them?
What kind of timing?, what kind of boost? What kind of cost? More details on the 16 steps. I assume its like the Caspers Ultra chip, but with more steps.

 

[LAWRENCE ELVOID]

2 months back I had a backfire on the low end and on the high end. I hope you have discovered your problem's answer with the tuneup. I did. I was going to change out the plugs and wires because (5) on the driver' side was notfiring. Number 2 plug wire was burn't almost in two places. The car still ran but not quick well past the speed limit. I HAD A CRACKED EXHAUST MANIFOLD and it caused the wire to be burned. There is no heat shield for the plugs on the 84T exhaust manifolds although the 85's have them. I replace the bad wires, made a heat shield to deflect the hot gases from the cracked manifold and now the car screams (flies) whenever I ask it to. These are some terrrific cars even when everything is not exactly right.
All turbo cars will bog down with even the smallest leak in the piping to the turbo. MAKE SURE all the piping is tight. I will have to loosen all the mounts for my eng/trans and slide the engine forward to remove the right side engine manifold and have the crack welded. Then put it all back together again.

 

[WFO]

Re: Max Effort Chip

Originally posted by Mr.Buick
Tell us more about the Max Effort Chip, where do you get them?

from steve yaklin
http://members.tripod.com/turboracer/maxeffort/

What kind of timing?

8 positions at 18º and 8 positions at 24º.fully adjustable street chip and race chip all in one.

what kind of boost?

as much or little as you want.you have to use a boost controller with the maxeffort(no ecm control).

What kind of cost?

$360.

More details on the 16 steps. I assume its like the Caspers Ultra chip, but with more steps.

i'm not familiar with the ultrachip,but from what i understand the maxeffort offers much more control over the tune of the car.everything is adjustable,and the different thumbwheel positions control fueling.check out the website.

later,sean