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1983 Cressida Hesitation

I have an '83 Cressida that I just inherited. The car has 154k miles,

5MGE (2.8L) and AT. The car has been sitting for the past 5 years, started 2-3 times, and never driven during that period. I want to get this car back on the road. I replaced all the fluids, new plugs, cap, rotor, wires, air filter and fuel filter. The engine starts easily and idles very well. I measure 22" of manifold vacuum at idle (rock steady on the vac gauge), and set the timing to 12 deg BTDC and verified the ECU timing advance is OK. The problem is a significant hesitation, and loss of power when the throttle is opened. When in park, the motor won't stall, but attemtping to drive the car, it willl stall, and will not get above 20 mph.

Anyone have any ideas as to where to start to diagnose this? I'll replace the O2 sensor, since it is original, and the motor will run better, although I doubt this is the cause of the problem. I may replace the TPS also, since it is also relatively inexpensive, and will also make the motor run better.

I don't want to replace the EGR or Air Flow Meter unless I am convinced that either/both will solve the problem. These parts are both quire expensive.

I sprayed the throttle bottle w/ Gumout to remove buildup.

Thank you.

- Glenn

Reply to
projman
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I do not recommend replacing parts without first checking their function.

Does the hesitation occur with the transmission in neutral or park or does the hesitation occur only under load?

What happens to manifold vacuum when you rev the engine?

When you replaced the cap, rotor, plugs, and wires, did you use OEM parts? I have seen problems like youa re describing with aftermarket ignition parts.

Check the plastic intake tube between the air flow meter and the throttle body for cracks and holes.

The EGR is relatively easy to check. With the engine idling, apply vacuum with a Mighty-Vac or by sucking on the vacuum hose leading to the EGR. The engine should start to stall if the EGR is functioning properly.

The air flow meter is basically a potentiometer. As air flows past the door (flap), it pushes the door open, and as the door opens, it sends more voltage to the ECU. If you measure voltage as you move the door by hand, voltage should go up proportionately.

Since the car has sat for so long, there is the possibility that the injectors are gummed up. I would try either the Toyota branded fuel injector cleaner that the Toyota dealer sells or Chevron Techron. Follow the directions on the can. If the injectors are badly clogged, they can be professionally cleaned.

If you have a fuel pressure gauge, you may want to check fuel pressure.

Reply to
Ray O

I would suggest to check the fuel pressure as well. I'd even suggest to check this out first. When a car sits for a while, there's a potential for the fuel pump to go bad.

Reply to
Viperkiller

Reply to
tom418

Ray -

Thx for your insight. Below are my responses to your comments.

The hesitation occurs in park and in gear. The motor will not hold any rpm above, or slightly above, idle. I inspected the duct work between the AFM and throttle body, and see/hear no leaks. Also, the vac gauge is rock steady at 22" at idle. I don't think my problem is a vac leak, or I'd see some movement on the vac gauge, or a lower reading at idle. I will check the vac gauge, when opening the throttle. The engine does not rev, so this test probably won't help. I will test the EGR w/ my Mighty Vac. Thx for that idea. I think it is a good idea (better MPG's) to replace the O2 sensor given that it is the original part that is 23 years old w/ 154k miles. My replacement parts are all aftermarket. I don't think the problem is ignition related. My feeling is that it is air/fuel delivery related, or an exhaust restriction. If the EGR checks out OK, I will disconnect the exhaust pipe at the exhaust manifold to confirm/rule out an exhaust restriction. Maybe my aftermkt fuel filter is bad, but highly unlikely. I will also hook up my fuel pressure gauge. My elec fuel pump is noisy. Is this normal for this car, or maybe an indicator that it's going bad??? I'd also like to test the AFM voltage as you recommend. I just bought a Chilton's book for this car on eBay. I hope this procedure is in the book. I'll also add some injector cleaner to the gas tank.

- Glenn

Ray O wrote:

Reply to
projman

The reason I asked about vacuum above idle is that I have seen some plastic T-connectors crack and leak only when revving the engine, where the rocking of the engine pulls on the connector enough to expose the crack. I've only seen this a few times, and frankly, it is not high on my list of probable causes.

I will test the EGR w/ my

I doubt if the EGR is the cause of the problem, but it doesn't hurt to check it out.

I think it is a good idea (better MPG's)

If you use an aftermarket O2 sensor that requires splicing wires, save the pigtail connector off of the old sensor and splice that so that you do not have to worry about the vehicle wire harness. I recommend soldering rather than crimping, and using shrink tubing for insulation.

My replacement parts are all aftermarket. I

An easier way to check for an exhaust restriction is use a thick rag or towel to block the exhaust at the tailpipe. The engine should run much worse is the exhaust is free from obstructions. If it is the same, then start looking for a restriction.

Maybe my aftermkt fuel filter

It has been a long time since I've ridden in an '83 Cressida, but I do not recall them having a noisy fuel pump.

By the way, there are 4 possible causes of low fuel pressure, in order of likelihood - bad fuel pump, bad fuel pressure regulator, restriction in the fuel filter, and a leak or restriction in the fuel line. It is possible, but unlikely, that fuel pressure will be OK but fuel volume is too low. The check for fuel volume requires a glass beaker like a chemist would use, and I forget the check - that is, how much volume over how long.

I'd also like to test the AFM

Good luck!

Reply to
Ray O

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