Loses power under acceleration


MikeS144
02-11-2009, 12:51 PM
Hey guys.

Having troubles with my 94 xFi. All of a sudden I am losing power under heavy acceleration. If I just rev the engine it does fine, nice and smooth but in gear, any gear, it just sorta falls on its face. It doesn't seem to be ingnition related as all the cylinders still fire (it doesn't miss) Replaced the fuel filter and tried running without the air filter, no difference.

I threw a set of spark plugs at it just for giggles, but it didn't make a difference. The old plugs were nice and clean.

Is there a service port that I am not seeing where I can check fuel pressure? I'm thinking this is fuel related.

By the way, the car has 316000 miles on it and I have never turned a screw on the TBI.

Thanks

Rooy
02-11-2009, 01:09 PM
My first thought was fuel pressure also. There is no port to check the pressure. The easiest place to tee in a gauge would be where the rubber hose meets the hard line at the firewall. The line going to the very front of the TBI is the inlet. I believe it's the line closest to the driver's side when you're looking at them on the firewall.

MikeS144
02-11-2009, 01:47 PM
Thanks I'll check that. Going to the parts store to rent/borrow a fuel pressure gauge. Is there another fuel filter other than the one at the tank that I am missing?

Rooy
02-12-2009, 02:11 AM
Nope, no other fuel filters.

carpenter_jai
02-12-2009, 02:34 AM
I would check your compression. 316000 miles is the most I have heard of on metro yet. Most of the metros I see that have died of old age don't make it past 250 000 miles. You want to have at least 150 lbs pressure to be barely good. Not so sure about the xFi, but for the 3 cyl engine, 200lbs pressure is preferred.

Jai

redpepe
02-12-2009, 10:49 AM
i would also replace the ignition wires which i've found produce similar low end lagging performance results when old. usually though you'll note a 'skip'. egr could be faulty too.

i'm still running mine .... '91, 3cyl .... and often pulling a trailer at 326,000 miles. the compression is way down in number 3 and part down in number 2. still uses zero oil!

MikeS144
02-12-2009, 11:54 AM
Checked fuel pressure. getting 17 pounds at idle. When I get on the throttle it drops to 15 or so and immediately returns. Under power (which is when it is acting up) it does the same. Grr.....

MikeS144
02-13-2009, 11:56 AM
update: replaced cap button and wires in addition to the plugs now. Put a timing light on it and drove it. Still getting spark, no change. thinking....injector?

brivers
02-13-2009, 08:07 PM
Does it sound the same as it did when it ran good? Does it start easy? I would look at two things, air going in and exhaust going out. Check for major vacuum leaks, then check for plugged catalytic converter or a crimped exhaust pipe.

MikeS144
02-14-2009, 08:54 AM
Is does sound the same, except for when it lays down of course. It is a little harder to start. She has always started a split second after hitting the key and now it takes about a second.

This morning I pulled the o2 sensor out and drove it. while I'm sure my neighbors appreciate my car troubleshooting at 730 on a Saturday morning, it didn't make a difference.

Square one.
Here is what she is doing.

car starts. car runs. under heavy throttle, car just kinda lays down. If I am in neutral it revs up just fine, only under load does it act up.

Here is what I have done so far.

1. Replaced fuel filter
2. Replaced plugs, wires, cap and button
3. Put a fuel pressure gauge in, pressure never drops below 17 psi (range is 13 to 20 psi)
4. Put a timing light on each wire and drove the car. Never lost spark on any cylinder.
5. Drove the car with o2 sensor out which made no difference. (rules out a plugged cat or other exhaust problems)
6. Checked EGR valve, it moves freely
7. Checked all over extensively for vacuum leaks, none to be found.
8. Oh yeah, drove the car with no air cleaner to rule that out.
)
I will be doing a compression check this afternoon (hopefully)

RossT
02-14-2009, 12:45 PM
Mike, I have a 93 but it should be the same as a 94 for fuel pressure.

My factory service manual, under section 6E (fuel system diagnosis) fuel pressure check.

Turn ign switch to lock
install pressure guage
turn ign swith to on, guel pump will run for 3 seconds
note fuel pressure
PRESSURE SHOULD BE 23-31 PSE WITH FUEL PUMP RUNNING, and holds after fuel pump stops IS IT?

The flow diagram in the FSM then spits according to your PSI

if fuel pressure below 23psi or above 31psi go to section......

if pressure below 23psi..

turn ign switch to on, check pressure while blocking (pinching fuel return line)
pressure should be 23psi or higher ist it?

if NO- check for leaks at hose connection to fuel pump in fuel tank
check for restricted fuel feed pipoe or fuel filter
if ok REPLACE FUEL PUMP

if YES replace fuel pressure regulator

RossT
02-14-2009, 12:49 PM
From reading the flow chart from the FSM, it sounds like you have pressure, but not enough. I had a metro once that would have a hard time making it up steep hills. Turned out to be fuel pump, it had pressure, but not enough.

MikeS144
02-15-2009, 08:29 PM
FIXED!!!! I was going to get a buddy of mine across town who happens to be a mechanic look at it with me today. As I am leaving the house I notice "hm, got less than a quarter tank, better fill it up." Stopped at the local Exxon and filled up. Got 2 miles down the road and all my problems went away! Drove the car an additional 60 miles, starting and stopping, interstate and all. No problems. BAD GAS!!!!!!!

RossT
02-15-2009, 08:56 PM
Good! now if your problems returns when she gets down to 1/2 tank or so you know where too look (inside the gas tank).
let us know if you have further problems.

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