escort_lx

Hi folks, got a 1990 sierra 2.0 twin cam with an annoying flat spot on acceleration, it sort of kangaroos when you accelerate through the flat spots, feels like something is restricting it.
Ive done plugs, leads, cap and arm, changed fuel filter, coolant temp sensor for the ecu, changed oil and filter, air filter. Had gunsons fault reader on it which flashes out all clear.
Anyone any other ideas what else i could check before i bin it n fit a pinto lol

boy-racer-1

This is an injection model isn't it? Check injectors and earthing points and if it's got an air flow meter that can cause problems too, possible fuel regulator for bad fuel air mixture

dojj

iTrader: (3)

the twinky don't have afm's

one of the common problems as they get older is the crank case breather valve under the exhaust manifold, or the pipe that links this to the inlet manifold around the back of the engine letting air into the system

it could also be a short in the tps, but you need to have the correct tps and then there's a specific way to refit and reset the base idle etc so it's not as simple as just undoing some screws

Mike Kerbey

iTrader: (1)

MAP sensor or vacuum hose going to it.

Cossiemainful

iTrader: (1)

Change the crank sensor located around the oil filter. Older plug seals and oil contamination over the years will may kill them or cause trouble.

escort_lx

Thanks, will give those things a check, i know the pipe to the map is good tho
Had it a run earlier n noticed its not so bad when engines cold?
Might try venting crancase to atmosphere n block the port on the inlet to rule that out.
Guess the crank sensor could be breaking down when its hot but it starts fine hot or cold ?

Cheers
Greg

dojj

iTrader: (3)

If its the cps it'll be the wiring getting covered in oil
They sit in such a comfy place it's not an issue
The crank case breather is the cheapest and easiest fix

escort_lx

Ok breather systems fine, crank sensor plugs fine with no oil in the connections, checked spark plugs and they look a bit on the lean side (white) guessing it must be fuel pressure related, the regulator has never been tampered with, wondering if it could be a weak pump? Also does anyone know what the inline filter looking type thing is on the return line for the fuel?

escort_lx

Had it in for mot today, emmissions were showing 0.17% co, thing must have been running on fresh air, turned potentiometer up to just under 3% and much better but still a bit chuggy when it gets hot, hope another tweak sorts it out

lime

check the earths had that problem added more earths that cleared it

GVK.

I'd check the fuel pressure when hot too.

Seem to remember a rubber pipe in the in-tank pump either splitting/ collapsing on these..back in the day.

escort_lx

Ive unplugged the coolant sensor and plugged another sensor in but just left it hanging on the wire so engine always thinks its cold, runs ok this way, will do for now until the pinto goes in

Cheers

Glenn_

iTrader: (1)

Why are you wanting to but a pinto engine in it.

dojj

iTrader: (3)

the pinto's can be tuned for more power far more easily and cheaply than the twinky can glenn

although the twinky is much better fuelwise each to their own

it's very hard to get bits for the later engine and your looking at around a max of about 140 brake with filters and chips and cams, or you can transplant the 2.3 engine in and as long as you've got aftermarket ecu's doing the ignition it's all good for around the same sort of money

or you can turbo it

escort_lx

I'm going pinto efi turbo

Glenn_

iTrader: (1)

Top info again Dojj. I think the twin cam engines are a good lump. I could never understand why they weren't 16v.

dojj

iTrader: (3)

they all came with 16v pistons though but the dohc was very very good on part throttle cruising, I've had 72 mpg from mine in the past and 40mpg is easy enough to get from them if they are looked after properly
They were designed to run hit though to maximize the economy but changing the fan switch to the Mondeo diseasal doesn't seem to effect that when it drops the fans by 10 degrees on each fan operation

escort_lx

Ok folks ive fitted the pinto engine now and the car has the exact same problem, guessing it must be the fuel pump as this is the only thing that hasnt changed in the conversion, i've got a fuel pressure gauge on order

Mike Kerbey

iTrader: (1)

lol that's pretty extreme fault finding. The 8v DOHC is a good unit, I don't see why you are so determined not to use it.

escort_lx

I was fitting a pinto anyway mate, just hoped it would cure the fault in the process, once its running properly i'm doing a budget turbo conversion, thers more info online and parts available to suit the pinto on this conversion than there is for the dohc unit, as you say tho its a step back in time i know

GVK.

escort_lx

Haha, right i've fitted inline fuel pressure gauge today and its running 29 psi, drops slightly when u rev up, tried removing vac line from the reg which i believe should increase the pressure at idle? And nothing happens, also tried crimping return line and pressure still stays same, pressure drops instantly when you switch off. Defo seems like the pumps pumped!
Am i correct in saying the pressure should be 2.5 bar? (36 psi)

GVK.

I would expect it to be 3 bar, but will see if I can find out.

Yes, removing the vacuum connection should raise it slightly.

GVK.

Delivery pressure 5.0bar
System pressure 3.0bar
Regulated pressure with vacuum 2.3 - 2.7bar

That's from Autodata, seems a bit odd, usually you get slightly more pressure without vac..

Even so, if yours is 2 bar, it's lower than above spec.

escort_lx

Thanks for the figures mate, yep the pressure should defo rise when vac is removed, it doesnt so i'm positive pump is on its road out

Cheers!

escort_lx

Got a replacement used pump now, ive removed the inline fuel damper from it as the seals look a bit iffy, guessing this could be the prob with the pump thats in it at the moment? Will removing this have any effect on how it runs? Its obv for the dohc engine but does the pinto need one?

Cheers